Google Desktop!

Google Desktop is now available. This is an amazing application that allows you to use Google search to find information on your local PC, including files, emails, web history, IM chats in a number of different formats. It integrates with the Google website, so search returns from Google web search appear alongside search results from your own PC. I just started using it, but thus far the search is extremely quick and accurate.

O'Reilly Network has an excellent review of the product, as well.