Larry Sanger is one of the two guys who founded Wikipedia. He had a difference of opinion with the other founder, Jimmy Wales, over the role experts would have in Wikipedia's content. As a result, he has announced an online encyclopedia called Citizendium. It will start as a fork of Wikipedia, but with be based far more on experts' contributions.
Mike (no last name) at Modern Dragons has a long and thoughtful piece about the prospects of Citizendium, with many links to other thoughtful pieces.
This is a long and nuanced story, involving complex themes of scholarship, community, and inter-personal conflicts between the two founders. Complicating the prognosis for Citizendium is the fact that a precursor to Wikipedia was an online encyclopedia called Nupedia, which relied more on experts than amateurs, and was founded by, you guessed it, Larry Sanger and Jimmy Wales.
It'll be very interesting to see how this plays out. Citizendium seems to be willing to go slowly (they plan to have a charter written within the year); the internet doesn't generally reward hierarchical structures; and it will be hard to "compete" with Wikipedia. But if it means we have a higher-quality encyclopedia, I'm all for it.