A really good free service you should try out is http://bit.ly - They provide also real time statistics for any url you shorten there. I think it's the best one out there !
Hootsuite offers its own URL shortening service . While this seems convenient, because you can just paste a long URL in for automatic shortening and insertion into your Tweet, there are drawbacks.
have a quick study of re-write engine software. Just I have listened about it and very curious to know more.