Some resources that offer quick answers to your questions include JustAnswer.com, Yahoo! Answers, Blurt It and Askville powered by Amazon. Of these, JustAnswer is the only site that answers questions with experts. Use it by asking a question and then creating an account at the prompt. Place a payment, and confirm it if the expert successfully answers the question; otherwise, it is refundable.
One of the most popular community question and answer sites is Yahoo! Answers. You can search for related questions or ask your own question. Visitors rate answers, and the best answer is displayed first below the question. Blurt It has a similar setup and allows questions without registration. Questions are organized into categories, which allows you to search similar questions and answers.
Askville by Amazon allows you to enter a question and then instantly, questions with similar subject matter pop up. If your question is unique, then you can post it for the community to answer. Email notifications inform you when you have answers waiting. The site encourages top users by giving out gold stars for questions and answers.
Another site is Ask Me Help Desk. This site requires registration to ask or answer questions, but it differs from others mentioned in that it allows you to get paid for answering questions, and you can establish an expert profile.