If you've gotten phoney emails claiming to be from the IRS, they've now set up an electronic mailbox to wihch suspicious emails can be forwarded. The email is phishing@irs.gov, but the IRS recommends that you first go to www.irs.gov for instructions. When you reach the IRS site, enter the term "phishing" in the search box in the upper right hand corner. then open the article "How to Protect Yourself from suspicious emails" to find the instructions. The IRS can use the information, URL's and links in the bogus emails to trace the hosting web sites and try to shut them down.
From KC Star article 4/10/06, by Albert B. Crenshaw of the Washington Post.