i've set up the wikipedia (wikimedia) one at work - i'd recommend this one over most others..
And I as well have set up Wikipedia, and find it a joy to use. It's a great way of getting down a lot of good data in a small amount of time.
And, if I do say so myself,
there's been a bit more data lately out there, and hopefully this will be the perfect opportunity to get one started.
Altough I have no capability to host one, I'd be happy to set up /administer / manage one elsewhere.
Ben