If you are using Firefox and have installed Greasemonkey, you can install a Greasemonkey script called Nofollow Display that will make all links on a page that use rel=nofollow show up as a strikethrough link. This can be very useful when evaluating a potential backlink. Sure, you could View Source, but it's nice to know at a glance. You can get Greasemonkey here and get the Nofollow Display script here.