For the time being I am an active user of the Ukrainian section of the Wikipedia (wikimedia) project. I am trying to extend the current level of description for topics like "Design Patterns", "Programming languages", "Intellectual Property" etc. I do that not merely to "do such a good thing for community" but because this way I am bringing up my own level of knowledge of such things. It's kind of learning form. I write something means I memorize something, something useful for me. Why not?
As yet I like that. It does cost the time, but... I like it :-)
As I am learning Esperanto, I plan to start to contribute to the corresponding part of wiki, just to drill the language skills (to the point, this blog is kinda language driller in English for me).