Bit.ly has been one of the most popular URL shortening services. It became more popular when Twitter chose it as the default URL shortening service. Bit.ly is a 5 character name, and in the URL shortening service it is essential to have as short name as possible. So, Bit.ly has powered a new URL shortening sercice, called J.MP
J.MP is exactly same as Bit.ly, only difference being that the name is 2 characters short than Bit.ly. This might not seem like a big deal, but it is indeed a big deal when such URLs are used in services like Twitter. Twitter imposes a 140 character limit on each tweet, and 2 additional characters mean a lot in that case.
If you have been using Bit.ly, it might be a good idea to try J.MP. You will get 2 extra characters for your tweets!