Three catalogues of the Archivo Histórico de la Universidad de Sevilla can be searched electronically. The start 1518, 1567, 1587.

General information on this can be found at http://fondoantiguo.blogspot.com/2007/11/catlogos-del-archivo-histrico-de-la.html .

Descriptions of the tree catalogues can be accessed via http://virtualbus.us.es/ahus/index.php .

The search interface is at http://virtualbus.us.es/ahus/formulario.php

Thanks to HCK at
http://www.phil-hum-ren.uni-muenchen.de/W4RF/YaBB.pl?num=1196414863

Update:
100+ digizited documents of the archive at
http://fondosdigitales.us.es/books/search/list_books_by_group?oid=8