Huginn - Build agents that monitor and act on your behalf. Your agents are standing by!
Visualping - Visualping is the easiest to use website checker, webpage change monitoring, website change detector and website change alert software of the web. Read more about Visualping.
Distill Web Monitor - Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.
PageProbe - Automatic Page Monitor - Create automatic monitors for detecting and scanning changes on web pages, evaluate content based...
Wachete - Track web page changes and get notified. Free Sign-up. Have all data in one place
Update Scanner - Update Scanner is a Firefox extension to monitor web pages for updates.