Of course it has been released, and it's been reported on Mac Rumors and every other tech web site today. However, it shows up earlier for some users than others, probably due to Apple staging the rollout, or maybe just the fact that the Intertubes are pretty clogged today.
You can download the IPSW file yourself (look in the main iPhone forum or the MacRumors front page or TUAW or Digg or really anywhere for the link) and do a forced restore, but if you're not the power user/fiddler type you should probably just wait until iTunes gives you the go-ahead.