George Hotz had released purplera1n Jailbreak app for the iPhone a few days ago, and was the first one to do it. The app was initially released on Windows, then updated to run on Windows 7. Now, with the help of some friends, he has released it for the Mac. The instructions are the same, but go to the purplera1n and click on the Apple icon to download the Mac version of the app.

Detailed installation instructions

purplera1n Download Link