I've been following Jeff Atwood and Joel Spolsky's new creation stackoverflow since they started blogging about it, and so far I'm pretty impressed.
If you haven't visited, it's a programming-specific forum with a karma system like slashdot's, a voting system like digg's, and a collaborative environment like wikipedia's.
It's already turning out like an experts-exchange that actually works. (Don't get me started - I've thought experts-exchange.com was the smarmy-est type of internet pollution for years)
It's still in public beta, and they're still ironing out some wrinkles, but I like it so far. Joel and Jeff have been really up front with their development efforts, and Scott Hansleman has even given them some helpful advise about how they're using MVC in a podcast.
Oh, speaking of pod casting, Joel and Jeff have been putting out their own on stackoverflow (via IT Conversations). I've listened to 4 of them now, and they're pretty cool. The problems they've been facing getting the karma system working are neat, and some of the technical hurdles are interesting.
I've been playing around with stackoverflow for a while now, and I've asked and answered some questions. It seems great for detailed programming questions, but architecture issues don't get a lot of traffic.