I found some mailing lists and message boards just by looking up keywords of subjects I was interested in, but in Spanish. Spanish Photoshop and graphics message boards, art message boards, pulp novel fans, that sort of thing. I’m only active on a few of them (that’s enough!) but the people are very understanding. They think it’s great that I’m trying to learn their language and I actually do have something of worth to say (in my crappy, broken Spanish) about the topics being discussed. I definitely try not to monopolize the discussions, though, because the group does not exist to educate me and I don’t want to wear out my welcome.
I’d love to join some Spanish language groups or message boards for people who are learning the language. A while ago someone gave me a link to one (I know I bookmarked it) and I’d like to find more.