Using Gmail as a Spam Filter

Reader Gmail100 left a great comment to How Secure is Your Web-Mail? pointing to How to use GMail as FREE Hosted Anti Spam Filter Software which provides details on using GMails strong spam filtering to set up a

simple and free solution for companies, organizations and individuals who want to get rid of spam without buying and maintaining their own anti spam server or anti-spam software.

This is pretty similar to what I am doing, except I use Gmail's imap service. Thanks Gmail100!