Stackoverflow is one of the best Question & Answer websites for computer programming. It uses a carefully designed social model to build a community where people compete to give the best answer to questions in order to be rewarded with a better response to their own questions.
Recently, the people behind Stackoverflow have opened up the software to allow people to set up their own websites...but just for a beta period (money will then be required). Several chemistry 'stackoverflows' have already been set up. Here are a few I've heard about:
BlueObelisk: Questions about cheminformatics and computational chemistry leaning towards the open source or open data side of things. Update (07/10/2010): This website has moved to Shapado.
Chempedia Lab: Questions about experimental chemistry.
Chemistry: General chemistry (?)
These sites are all new so you won't find many questions there already. But give them a go. Go there and ask a question or two (even if you already know the answer), answer a question or two, and check back in a day to see what happens. You can log in with your Gmail address (among others) but do note that questions are not anonymous.
Such websites require a community. Some will gain such a community and flourish, others won't and will fail. In the meanwhile, go get some answers.
Image credit: Duncan Hull