Hi!

First of all - do you speak spanish? that's quite important question.

If yes, there are several places to check. Loquo webportal www.loquo.es has separate site for internships. Also www.infojobs.net has a section for "practicas". Then you can approach recruitment agencies, i got my internship from talent search people www.talentsearchpeople.com - they offer special help for job seekers who don't speak spanish.

Be prepared though - here it's common that you don't get paid when doing an internship.