Yes, 19 year old George Hotz who you might remember shot to hacking fame a couple of years back when he claimed to be the first to unlock the original iPhone, has done it again. His 'purplera1n' software has been made available for immediate download, although it remains in Beta, and is said to be able to successfully jailbreak the new iPhone 3GS.
There are some problems though, not least that at the moment only Windows users can use it which is a little ironic given the core Mac fanbase for all things Apple, including the iPhone. Otherwise, as long as the device is running the 3.0 firmware and you have iTunes 8.2 installed you are good to go.
Amazingly, Hotz has produced an executable which is smaller than a C++ 'hello world' app yet will simply and speedily open up a 3GS device to non-Apple approved applications.
Hotz says "Normally I don't make tools for the general public, and rather wait for the dev team to do it. But guys, whats up with waiting until 3.1? That isn't how the game is played. We release, Apple fixes, we find new holes."