Bit.ly, the default url-shortener for twitter, has just launched a new site j.mp (saving two whole characters; I know you were counting) which will apparently replace bit.ly.

Moments ago I was automatically redirected from bit.ly to j.mp, then after trying again a few times I received a error message from Firefox saying that the redirect would never resolve. Then the Bit.ly link worked again.

My next test was to try to see if a bit.ly link would resolve if changed to j.mp and it does. www.bit.ly/1HMSZ2 and www.j.mp/1HMSZ2 are equivalent. And if you go to bit.ly and j.mp you'll see that other than the logo the pages look the same.

Looks like a permanent replacement is in the works.

Update:

Bit.ly has confirmed J.mp launch but not a permanant move. Then why test a redirect from Bit.ly to J.mp? Maybe they're waiting for brand recognition and trust to build up for j.mp before flipping the switch? That's my guess anyway.