I’m one of the beta testers for Stack Overflow, and I love it.
Stack Overflow is a community for programmers to ask and answer questions. So simple, yet so elegant. You can vote up questions and answers. You gain reputation points for having your questions/answers voted up. Gaining reputation points gives you more options – the ability to vote down, to retag others’ posts, and edit others’ posts. You can earn badges for your contributions to the community. It’s a lot of fun.
Jeff Atwood first described Stack Overflow in this post. He and Joel Spolsky are the creators – you can read Joel’s thoughts and sign up for the beta here. You can also read what Robert Scoble has to say.
If you’re even remotely interested, I’d recommend signing up for the beta – it gives you the chance to check it out and make suggestions for improving the site. It’s already really cool, and it can only get better – I can’t wait till it goes live.