I liked Tr.im. It was may favorite URL shorting tool. The home page now says they have closed and will be completely gone by the end of the year. See: Tr.im R.I.P. The reason? Spammers. Too many companies were using Tr.im to push their advertising and get around various spam blockers.
The ‘Thanks for all the fish.’ page provides a list of services you can use as replacements. Since I’m a Twitter kid I decided on bit.ly.