There are tons of platforms for building communities, i have been searching all around and i think the best would be to go with an open source platform, i am evaluating buddypress new community module by automatic the guys behind wordpress,it seems pretty solid, i tried also Drupal but i see it is very complicated.
What would you recommend to use that is flexible and were i could create modules and things constantly, i don't want to get into a paying a lot to start.