In October this year, the fourth International World Conference on Open Source will take place in Malaga :
http://www.opensourceworldconference.com/
I attended the previous two editions and the conference is well worth the visit : a lot of eminent speakers (see website of the previous editions) and very well organised.
Additionally, the location is superb : a beautifull congress centre and a city that is situated in a mediterrian climate ... ;-)
Jan