Large means: more than 100 works printed before 1800 in English, Latin, French, German, etc. (no Slavic languages) which are whooly digitized as facsimiles. I have estimated the numbers if they are not provided by the website.

For smaller digital libraries see
http://wiki.netbib.de/coma/DigiMisc and subpages
http://de.wikisource.org/wiki/Digitale_Sammlungen (digital libraries with at least 1 PD German book)

See also

http://books.google.com

http://www.archive.org/details/texts

http://www.biodiversitylibrary.org/

http://www.rarebookroom.org

AUSTRIA (1)

Innsbruck, University Library
http://www.literature.at

ESTONIA (1)

Tartu, University Library
http://dspace.utlib.ee/

FRANCE (8)

Nanterre, Library André Desguine
http://www.bibliotheque-desguine.fr/desguine/Bibliotheque-virtuelle?lang=fr

Paris, Bibliothèque interuniversitaire de Médecine (BIUM)
http://www.bium.univ-paris5.fr/histmed/medica.htm

Paris, Institut national de l'historie d'art
http://bibliotheque-numerique.inha.fr

Paris, National Library
http://gallica.bnf.fr/

Strasbourg, University Louis Pasteur, Library
http://num-scd-ulp.u-strasbg.fr:8080/
http://docnum.u-strasbg.fr/

(Troyes, BM is offline until 2010.) See below

Toulouse, University Library
http://tolosana.univ-toulouse.fr

Tours, Bibliothèques Virtuelles Humanistes
http://www.bvh.univ-tours.fr/index.htm

e-corpus - Cooperative Project
http://www.e-corpus.org/

GERMANY (23)

Augsburg, University Library
http://www.bibliothek.uni-augsburg.de/dda/

Berlin, Max Planck Institute for the History of Science
http://echo.mpiwg-berlin.mpg.de

Berlin, Staatsbibliothek
http://digital.staatsbibliothek-berlin.de/dms/

Braunschweig, University Library
http://www.digibib.tu-bs.de/

Darmstadt, University Library
http://www.ulb.tu-darmstadt.de/angebot/medien/digitale_sammlungen_1/digitale_sammlungen.de.jsp

Dresden, University Library
http://digital.slub-dresden.de/

Düsseldorf, University Library
http://digital.ub.uni-duesseldorf.de/

Emden, Johannes a Lasco Libryary
http://hardenberg.jalb.de

Frankfurt, University Library
http://sammlungen.ub.uni-frankfurt.de/
http://edocs.ub.uni-frankfurt.de/

Göttingen, University Library
http://gdz.sub.uni-goettingen.de/

Heidelberg, University Library
http://www.ub.uni-heidelberg.de/helios/digi/digilit.html

Halle, University Library
http://bibliothek.uni-halle.de/dbib/digital/

Jena, University Library
http://archive.thulb.uni-jena.de/hisbest/content/below/index.xml

Kiel, University Library
http://dibiki.ub.uni-kiel.de/
http://www.ub.uni-kiel.de/digiport/bis1800/altdruck.html

Köln, University Library
http://www.ub.uni-koeln.de/digital/digitsam/index_ger.html
http://inkunabeln.ub.uni-koeln.de/

Mannheim, University Library
http://digi.bib.uni-mannheim.de/
http://www.uni-mannheim.de/mateo/camenahtdocs/camena.html

München, Bayerische Staatsbibliothek
http://www.digitale-sammlungen.de/

München, University Library
http://epub.ub.uni-muenchen.de/view/malte/malte.html

Münster, University Library
http://sammlungen.ulb.uni-muenster.de
http://miami.uni-muenster.de/

Weimar, Herzogin Anna Amalia Library
http://ora-web.swkk.de:7777/digimo_online/digimo.entry

Wittenberg, Lutherhalle
luther.hki.uni-koeln.de/luther/
[temporarily (?) offline since 2010]

Wolfenbüttel, Herzog August Bibliothek
http://www.hab.de/bibliothek/wdb/

VD 17 - Cooperative Project
http://www.vd17.de/
Search for: volldigitalisat

HUNGARY (1)

Budapest, National Library
http://mek.oszk.hu/indexeng.phtml

ITALY (4)

Firenze, Institute and Museum of the History of Science
http://fermi.imss.fi.it/rd/bd

Milano, University
http://www.historia.unimi.it/scripts/diglib/digliblista.php

Roma, Bibliotheca Hertziana
http://rara.biblhertz.it/

Torino, University
http://www.opal.unito.it

JAPAN (3)

Kirishita Bunko, Sophia University
Laures Virtual Rare Book Library
http://133.12.23.145:8080/html/index.html

Osaka, City University
http://libweb.media.osaka-cu.ac.jp/els-e.html

Tsukuba, University Library
http://www.tulips.tsukuba.ac.jp/pub/tree/kichosho.eng.html

NETHERLANDS (2)

Leiden, University
http://www.let.leidenuniv.nl/Dutch/Renaissance/Ursicula.html

Utrecht, University Library
http://objects.library.uu.nl/reader/object_list.php

POLAND (4)

Gdansk, Library of the Polish Academy of Sciences
http://dlibra.bgpan.gda.pl/dlibra

Wroclaw, University Library
http://www.bibliotekacyfrowa.pl

Warszawa, National Library
http://www.polona.pl/dlibra/collectiondescription2?dirids=17

Digital Library of Wielkopolska - Cooperative Project
http://www.wbc.poznan.pl/dlibra

PORTUGAL (3)

Coimbra, University Library
http://almamater.uc.pt/

Lisboa, National Library
http://purl.pt

Lisboa, University
http://www.fl.ul.pt/biblioteca/biblioteca_digital/index.htm

SPAIN (18)

Bilbao, Provincial Library
http://www.bizkaia.net/kultura/foru_liburutegia/bibdigital_spi.asp?Tem_Codigo=2542

Granada, University Library
http://adrastea.ugr.es/search*spi~S2
http://digibug.ugr.es/handle/10481/163

La Rioja, Provincial Library
http://bibliotecavirtual.larioja.org

Madrid, Royal Botanical Garden
http://bibdigital.rjb.csic.es

Madrid, National Library
http://bibliotecadigitalhispanica.bne.es

Madrid, Universidad Autónoma, Library
http://digitool-uam.greendata.es/R

Madrid, University Complutense
http://cisne.sim.ucm.es/search*spi~S4/e?SEARCH=biblioteca+digital

San Millan, Fundación San Millán de la Cogolla
http://www.fsanmillan.es/biblioteca/biblioteca.jsp (May, 2012)

Santiago de Compostela, University Library
http://iacobus.usc.es/search*gag~S7

Sevilla, University Library
http://bib.us.es/nuestras_colecciones/fondos_digitales-ides-idweb.html

Valencia, Biblioteca Valenciana
http://bv2.gva.es/

Valencia, University Library
http://biblioteca.uv.es/valenciano/recursos_electronicos/somni.php

Zaragoza, University Library
http://roble.unizar.es/

Cooperative Projects in Spain:

Biblioteca Virtual Andalucia
http://www.juntadeandalucia.es/cultura/bibliotecavirtualandalucia/inicio/inicio.cmd

Biblioteca Virtual de Derecho Aragones
http://www.bivida.es

Biblioteca Virtual de Patrimonio Bibliográfico
http://bvpb.mcu.es

Biblioteca Virtual Lastanosa
http://bv.lastanosa.com see Biblioteca Virtual de Derecho Aragones

Biblioteca Virtual Miguel de Cervantes
http://www.cervantesvirtual.com

Memorial Digital de Catalunya
http://mdc.cbuc.cat/index.php

SWEDEN (2)

Stockholm, Royal Library
http://libris.kb.se/
NB: This is the Swedish Union Catalog. Look at the subset "LIBRIS-bibliotekens digitaliserade material" when searching mat:(ebok)

Umeå, University Library
http://rara.ub.umu.se

UCRAINE (1)

Kyiv, National Taras Shevchenko University Library
http://www.rarelib.undp.org.ua/eng/index.php3
[temporarily not available]

UNITED KINGDOM (2)

London, British Library
http://www.bl.uk/treasures/festivalbooks/homepage.html

London, Warburg Institute
http://warburg.sas.ac.uk/library/digital-collections/

UNITED STATES (7)

Charlottesville, University of Virginia Library
http://www2.lib.virginia.edu/rmds/portfolio/gordon/completed_titles.html

Dallas, Theological Seminary Library
http://rarebooks.dts.edu/

Cambridge, MA, Harvard University Library
http://ocp.hul.harvard.edu/
http://lms01.harvard.edu/ (OPAC)

New York, Cornell University Library
http://digital.library.cornell.edu/

Pittsburgh, Carnegy Mellon University, Library
http://posner.library.cmu.edu/Posner/

Urbana Champaign, University of Illinois, Library
http://illinoisharvest.grainger.uiuc.edu/collections.asp?ctype=digibk

Washington DC, Library of Congress
http://www.loc.gov/rr/rarebook/digitalcoll.html

Update March 2010

SWITZERLAND

http://www.e-rara.ch/ - Cooperative Project

FRANCE

BM Troyes (online again)
http://patrimoine.agglo-troyes.fr
[In 2014 offline again]

UCRAINE

http://www.rarelib.undp.org.ua/eng/index.php3 is online again

RUSSIA

Russian State Library
http://elibrary.rsl.ru/?menu=s35/elibrary/elibrary4483/elibrary44834485/&lang=en

AUSTRIA

Austrian National Library
http://www.onb.ac.at/sammlungen/siawd/bibeldigitalisierung.htm


Update April 2010

SPAIN

RODA Patrimonio Bibliográfico Extremeño (Spanien)
http://roda.culturaextremadura.com/ - Cooperative Project

Murcia, University Library
http://digitum.um.es/xmlui/handle/10201/5

Update May 2010

POLAND

Warszawa, Faculty of Journalism and Political Science
Digital Library of Polish and Poland-Related News Pamphlets
http://cbdu.id.uw.edu.pl/

Update December 2010

ROMANIA

National Digital Library
http://digitool.bibnat.ro:8881

Update January 2011

GERMANY

Karlsruhe, Landesbibliothek
http://digital.blb-karlsruhe.de/

Koblenz, Landesbibliothekszentrum
Dilibri
http://www.dilibri.de/

JAPAN
Yokohama, Kanagawa University
http://klibredb.lib.kanagawa-u.ac.jp/dspace/browse-date?order=oldestfirst

SPAIN
Salamanca, University Library
http://gredos.usal.es/

Update March 2011

GERMANY

Marburg, Universitätsbibliothek
https://opac.ub.uni-marburg.de/CMD?ACT=SRCHA&IKT=1007&TRM=nel*dwb

Oldenburg, Landesbibliothek
http://digital.lb-oldenburg.de/

SPAIN

Biblioteca Virtual del Principado de Asturias
http://www.bibliotecavirtual.asturias.es

Biblioteca Digital de Castilla-La Mancha
http://bidicam.jccm.es

Biblioteca Dixital de Galicia
http://www.galiciana.bibliotecadegalicia.xunta.es

Update: June 2011

NETHERLANDS

Early Dutch Books Online
http://www.earlydutchbooksonline.nl/
[now: http://www.delpher.nl/ ]

Update: September 2011

GERMANY

Stuttgart, Württembergische Landesbibliothek
http://digital.wlb-stuttgart.de/

Update: May 2012

GERMANY

Bamberg, Staatsbibliothek
http://www.bayerische-landesbibliothek-online.de/bamberger-schaetze

Erlangen, University Library
http://bvbm1.bib-bvb.de/R/?local_base=UBE

Regensburg, University Library
http://bvbm1.bib-bvb.de/R?local_base=UBR

Update: December 2012

BELGIUM

Flandrica - Cooperative Project
http://www.flandrica.be

Gent, University Library
http://search.ugent.be/ (Google Books)

FRANCE

Lyon, Bibliothèque Municipal
http://numelyo.bm-lyon.fr/

UNITED KINGDOM

Oxford, Bodleian Library
http://solo.bodleian.ox.ac.uk (Google Books)

Update April 2013

NETHERLANDS

Den Haag, Royal Library
http://boeken1.kb.nl/ (Google Books)
[now: http://www.delpher.nl/ ]

Update May 2013

AUSTRIA

Vienna, National Library
http://www.onb.ac.at/bibliothek/digitaler_lesesaal.htm (including Google Books)

GERMANY

Leipzig, University Library
http://histbest.ub.uni-leipzig.de/

ITALY

Internet Culturale - Cooperative Project
http://www.internetculturale.it/

UNITED KINGDOM

Warwick, University Library
http://contentdm.warwick.ac.uk/

Update October 2013

FRANCE

Strasbourg, BNU
http://www.numistral.fr/

Update: November 2013

GERMANY

Hamburg, University Library
http://www.sub.uni-hamburg.de/recherche/elektronische-angebote/digitalisierte-bestaende.html

Update: December 2013

AUSTRIA

Vienna, University Library
https://phaidra.univie.ac.at/

GERMANY

Bonn, University Library
http://s2w.hbz-nrw.de/ulbbn

Coburg, Landesbibliothek
https://katalog.landesbibliothek-coburg.de/

Erfurt/Gotha, University and Research Library
http://archive.thulb.uni-jena.de/ufb/content/below/index.xml

Fulda, Hochschul- und Landesbibliothek
http://fuldig.hs-fulda.de/viewer/browse/

Greifswald, University Library/Digitale Bibliothek Mecklenburg-Vorpommern - Cooperative Project
http://ub-goobi-pr2.ub.uni-greifswald.de/viewer/

Tübingen, University Library
http://idb.ub.uni-tuebingen.de/digitue/tue/

ITALY

Rome, Biblioteca Apostolica Vaticana
http://www.vatlib.it/home.php?pag=inc_digitalizzati

JAPAN

Tokyo, University, Library of Economics
http://www.lib.e.u-tokyo.ac.jp/english/?page_id=3589

SPAIN

Navarra, University Library
http://dspace.unav.es/dspace/handle/10171/4687

UNITED KINGDOM

London, British Library
http://explore.bl.uk/

Update: February 2014

NORWAY

National Library
http://www.nb.no/English

Update: December 2014

GERMANY

Berlin, Deutsches Historisches Museum
http://dhm.de/datenbank/dhm.php?seite=6&db=0&fld_1a=volldigitalisate+rara

Update: April 2015

SPAIN

Barcelona, University Library
http://bipadi.ub.edu/

Update: September 2015

NETHERLANDS

Nijmegen, University Library
http://wwwextern.ubn.ru.nl/BookReader/Voortgang/Voortgang_project_scannen_Erfgoed.htm