This sounds very similar to what my company already does: http://hubpages.com

Google Knol has not done well in this space: http://news.ycombinator.com/item?id=757287

America Online seems to be shooting for something similar: http://www.techcrunch.com/2009/07/29/aol-newsroom-now-has-wo...

There's also squidoo and mahalo. Mahalo has recently done quite well in terms of growing traffic: http://www.quantcast.com/mahalo.com

It will be very interesting to see what startups emerge from this!