I would like to monitor a few websites that I use daily for changes. One of these is PayPerPost.com, which requires authentication to view the page I wish to keep updated on. Is there any freely available code to check a webpage for updates, and publish these updates as Rss or Atom? A public online service won't work because I have to be logged in to access the page. Alternatively, is there a way to create a desktop unix script that will check a page for changes and alert me (by playing a sound, beeping, etc.)?