Update Scanner
Open Source
Update Scanner is a Firefox addon to monitor web pages for updates. Useful for websites that don't provide Atom or RSS feeds.
WebSite-Watcher
Commercial
WebSite-Watcher detects website updates and highlights all changes in the text.
Compare ChangeMon.Com with alternatives
Compare Update Scanner and ChangeMon.Com and decide which is most suitable for you.
Compare WebSite-Watcher and ChangeMon.Com and decide which is most suitable for you.