Mahalo is sort of a commercial competitor to Wikipedia. Jason Calcanis, the founder and CEO of Mahalo, promotes Mahalo as an alternative to Google -- but it looks a lot more like Wikipedia to me!
One important difference, at least for now, is that you can add dofollow links to Mahalo. All Wikipedia links are rel="nofollow".
Read the details at New Mahalo features: anyone can edit (even if not logged in) and anyone can create a new page (easily).
It looks like Mahalo has been having trouble finding writers at the very low rates they are offering!
This is all the better for us serious SEO's.