Feeds make it easy to follow updates to all kinds of webpages, from blogs to news sites to Craigslist queries, but unfortunately not all pages on the web have feeds. Today, Google is rolling out a change in Google Reader that lets you create a custom feed to track changes on pages that don’t have their own feed.
http://googlereader.blogspot.com/2010/01/follow-changes-to-any-website.html