Moodle is perhaps one of the most successful case of libre software adoption in Spanish Universities. It is an Open Source Course Management System (CMS), also known as a Learning Management System (LMS) or a Virtual Learning Environment (VLE). It has become very popular among educators around the world as a tool for creating online dynamic web sites for their students. To work, it needs to be installed on a web server. Moodle is distributed under the GPLv2 license.
In oficial Moodle site you can find a list of the Spanish sites registered as users of Moodle. I counted 33 Spanish Universities sites there (its quite much if we think that in Spain there are 74 Universities).
However, registering is not mandatory so we can suppose that other Universities also use this e-learning system. The University of Murcia made a study in 2008 about the use of libre software e-learning platforms in virtual campus, resulting that 64\% of the Spanish Universities use a libre software product for their virtual campus, and Moodle is the most used product with a 53,3\% share. As a result of this study, they also made an interactive map of Spain where you can learn about libre software virtual campus in Spanish Universities.
I use Moodle myself as student in Universidad Rey Juan Carlos (Master of Libre Software) and also for several training courses at my job in Universidad Politécnica de Madrid.