Short URLs

http://makeashorterlink.com/

http://tinyurl.com/

http://snipurl.com/ (also http://snurl.com/)

http://notlong.com/

http://quickones.org/

http://qwer.org/

http://shorl.com/

http://shorterlink.com/

Perl API
WWW:Shorten

Other Directories
http://notlong.com/links/

http://directory.google.com/Top/Computers/Internet/Web_Design_and_Development/Redirects/