The Colorado Attorney General's office now offers an identity theft repair kit on-line. It offers tips on preventing identity theft as well as a check list on what you need to do if you are a victim of identity theft. While the phone numbers and addresses given are specific to Colorado, the advice in this 28 page booklet probably applies to you no matter where you live. Here's a link directly to the PDF version of the booklet:

http://www.ago.state.co.us/idtheft/idtrk.pdf