Volunteer opportunities in Barcelona
publicado por Usuario eliminado en Foro de Barcelona
I found this list, though it mixes volunteer work with internships and whatnot:
http://www.volunteerabroad.com/listings.cfm/countryID/82/cit
yID/1637The most common one seems to be Coined, here: http://www.coined-spain.org/Volunteer-Abroad-Spain/volunteer
-abroad-spain.htmlHope this helps