For programming-related questions and answers, check out stackoverflow.com, which launched today with a public beta. It looks very interesting - a forum, crossed with digg (user-rated), wiki capabilities (user-edited), and delicious (tags). The hope is that these three mechanisms will make the site more valuable over time, as questions are answered, rated, tagged, and edited for clarity.
Currently, the site is a bit Microsoft-heavy. For example, C# has twice as many questions as Java, and EMF refers to the vector graphics "Enhanced Metafile Format". Still, Eclipse is well represented with 58 questions compared to Netbeans with 5.
I find it amazing to watch how questions come in at a rate of roughly one per minute, and how they get answered at a similar rate. It's just like on the EMF newsgroup, but so much more Web 2.0!