Historical Dictionary of Spain
Scarecrow / NetLibrary.
Available online. (W&L subscription)
Second edition (2008) contains over 700 alphabetically-arranged entries on: "major Spanish organizations, including political parties, trade unions, and state bodies; the various regions and languages which comprise Spain, including Catalonia and the Basque Country; and major figures in Spanish culture and the arts."
Links will be maintained in several locations in the library Web site, including here.