Popular, but not entirely sure why it is superior... certainly not the shortest URLs but definitely one of the most reliable.

Where would Fitman be without it?

I use TinyUrl all the time to shorten links for posting to places like Twitter and RateItAll. Supposedly there's a really cool Firefox extension somewhere that lets you do it right from your browser, but I haven't tracked it down yet.

One of the most popular services, offering free short URL for all purposes. This address URL will not break in email postings and never expires.
The format is http://tinyurl.com/XXX
You can request the certain custom information, and if the subdoain is available you get it, for example, when I asked for nesher, I got the short URL http://tinyurl.com/nesher.