ServerFault.com is a new site that describes itself as "a collaboratively edited question and answer site for system administrators and IT professionals." It's free and no registration is required. The site is kind of like a cross between Yahoo Answers, Wikipedia, and Digg. Anyone can ask questions on the site. Other users can vote questions up or down and that affects how visible the question is on the site. As users answer questions, those answers can be voted up or down and marked as "the answer". All questions and answers can also be edited like a Wiki. What you end up with when you run accros the site from google is usually the question your looking for and right below it the best answer to the problem. Unlike forums where the best answer is the last post in the thread or burried in the middle. Plus if the something changed and a once correct answer is no longer valid then the correct answer can be edited to be made correct again. The site was basically built because the developers hated the spamy nature of Experts Exchange and how it always ranked high in Google for their own questions they searched for. You can read the FAQ (http://serverfault.com/faq) or the About page (http://serverfault.com/about) for more details. [more]
I've been using Server Fault's sister site for a while now while and have found it really useful. It's URL is StackOverflow.com and it's geared toward software developers. It started up late last year and already has over 190,000 questions. Server Fault has been up for less time and only has around 6,000 questions, but it has the potential to take off like Stack Overflow.