JoeBot is a generic web crawler implemented as a collection of Java classes which can be used in a variety of applications, including resource discovery, link validation, mirroring, etc. It currently limits itself to one visit per host per minute.
Check Favorites is a full-featured solution for maintaining all of the Internet-based links in your Favorites list (bookmarks). Check Favorites can check multiple links simultaneously and can optionally remove all of the broken links for you. Check Favorites also supports the ability to export your Favorites in a variety of formats, as well as the ability to extract, check, and export the links contained on any HTML page on your system, or accessible via the Internet (thus acting like a kind of link checker and ripper).