When you find yourself wishing you had a tutor to guide you through a difficult math problem or help you with an essay question, don't be sad because there are some online services that can help you for free.

Yahoo! Answers is a free site that allows users to ask questions and receive answers from other users.

Ask A Librarian is a service that allows you to ask a question and receive an email response from a librarian.

Ask a Math Tutor will try to answer your math questions within twenty-four hours. All questions are answered by email.

Ask Mr. Calculus - get a response on one calculus question per day with this online service.

More sites you can find here.