User Generated Content CMS?

This isn't necessarily a BH tool, though it may get used as such

I'm looking for recommendations on a CMS or script for setting up a site where like squidoo or hubpages users can create accounts and build their own pages around keywords in an easy manner and that isn't as stiff and hard to customize as wiki engines.

I appreciate any thoughts you care to share, thanks

There are several that exist out there, the first that comes to mind is Alstrasoft..but they blow. It would be nice to have a very flexible user generated CMS that is not centered around any specific type such as video. Me and my buddy have just launched the next you*tube but for audio...I'm not gonna plug it because it's my first post...but we had to have someone create a script from scratch because there aren't any customizable scripts like you speak of.