Use this page to enter any long url, then copy the shortened one in your texts, IM's, tweets etc. Send it, and when your receiver visits it, they are taken to the original location.
Useful in emails too because long urls can get broken over multiple lines.
Can be used as a regular url shrinker but is especially useful for mobiles because:
Creates ultra short URLs
Easy to remember - "Over The Air cc"
Can save you money, e.g. long urls in texts can go over the 160 char limit
Saves bandwidth - less data transmission cost, and faster
API available for mobile apps
With an account you get mobile stats, like which handsets visited your URLs etc