For those of you regularly turning to Google for answers to your programming woes, you'll find StackOverflow to be essential in day-to-day development. In fact, due to the popularity of the relatively new site, you've most likely come across many questions and corresponding answers within the Google results - often ranking very high.
The site itself is very clean and easy to use and after a few visits you'll soon pickup how it all works. I've been a member for just over 4 months, but have only clocked up a reputation of 121 - as I'm more of a reader than contributor.
On the flipside, there is now ServerFault from the creators of StackOverflow - Joel and Jeff. It's geared towards the system administrators out there, to discuss server memory configurations and connecting to SQL Server 2008. As I take a keen interest in the hardware side of things too, ServerFault is a great read for me too, but my reputation is even lower.
So, if you're not already using StackOverflow and/or ServerFault then start navigating there now. If not, you'll be seeing more of them both as the content from the community grows and is crawled by search engines more and more.