Yahoo! Answers is great for establishing professional credibility

http://answers.yahoo.com

This is a new service, free for charge, by Yahoo!

I highly recommend it to professionals, consultants, entrepreneurs, etc. who have expertise and want to share their expertise with others (including clients, partners, collaborators, suppliers, etc.).

In fact, I think that eventually every professional worth his/her salt, and every company that is serious about serving customers, will have a free Q & A section on their site where they answer customers and prospects' questions.

Progressive.com is a good example of a company that truly understands "customer service." They help people who have not even become customers! (By showing competitive rates and offers, which help people save time).