Specto is a desktop Python application that lets you monitor changes to static or dynamic web pages and then trigger notifications. Specto is perfect for websites or web pages that don't provide RSS/Atom feeds.
You can even configure Specto to monitor changes to files and folders on your own system!
For Ubuntu users, installation is as easy as pie, because Specto is in the Universe repository.
I'm so glad that I've found this alternative to Webmon. It's time to migrate all my monitored URLs to Specto now. ;-)