I'm sure many of you know about this already, but it's worth using if you pass links around. <a href="http://tinyurl.com/" rel="nofollow">http://tinyurl.com/</a>
In the spirit of TinyURL; <a href="http://www.hugeurl.com/" rel="nofollow">http://www.hugeurl.com/</a>. <p>It makes any url huge because Bigger is Better!
A couple of other services in the same vein: redirects where you get to choose the text instead of a random string at <a href="http://purl.org/" rel="nofollow">http://purl.org/</a> and quick posting of snippets of text or code at <a href="http://pastebin.ca/" rel="nofollow">http://pastebin.ca/</a> or <a href="http://dpaste.com/" rel="nofollow">http://dpaste.com/</a>