Freeware: AM-DeadLink

AM-DeadLink

"AM-DeadLink 1.42 - Freeware

AM-DeadLink detects dead links and duplicates in your Browser Bookmarks. If a Bookmark has become unavailable you can delete it from your Browser. AM-Deadlink checks Bookmarks from Internet Explorer, Opera and Netscape."

The 2.0 beta (also free) is cool... Export your fav's as a CSV, etc etc.

Very cool (using it right now) :)