Furies is a Java-based Web site testing tool which relies on many Jakarta components. Its goal is to ensure a Web page is "correct" by running one or more conditions on it. The Furies distribution supplies some conditions and it is very easy to program your own. For accessing Web sites, Furies relies on HttpClient and configuration may be done programmatically or via Digester.
Web Secretary is Webpage change notification (monitoring) software. It goes beyond the normal functions offered by such software by detecting changes based on content analysis, making sure that it's not just HTML that changed, but actual content. You can tell it what to ignore in the page (hit counters and such), and it can mail you the document with the changes highlighted or load the highlighted page in a browser.
Websitary is a script that monitors Web pages, RSS feeds, and podcasts and reports what's new. For many tasks, it reuses other programs (such as w3m, diff, and webdiff) to do the actual work. By default, it works on an ASCII basis, i.e. with the output of text-based Web browsers. With the help of some friends, it can also work with HTML.