This past August when I attended Wikimania, there were a number of other wiki organizations present and promoting their content. Two of the bigger wikis were:
I would thoroughly recommend one try out WikiHow. It is an excellent "how to do something" web service. Here are a couple of links ... some tongue and cheek:
With respect to the second wiki, CongressPedia ... it is really more of a political action group with liberal leanings. I reviewed the two senators from my state, Minnesota (Senator's Coleman and Dayton). As these two men are from different sides of the political spectrum, it was a good test of Congresspedia. Their entries are quite biased towards the "left". Thus, unfortunately, CongressPedia is not a very good source of information for the independent voter.