In a recent blog post by GeoHotz, he has put up an image of what seems to be a new "exploit" he just discovered for the iPhone 3GS (yeah, 3GS!).
Clearly depicted in the pic is a modified version of iBoot, which means he has somehow bypassed the sig check on the iBoot 596.24, which is the new one for the 3GS. The project he seems to be working on is what he calls "Purplera1n" or "purple rain" instead. He's even put up the site for it at http://purplera1n.com/ though all it sports is a pic of him with the phone, getting wet in purple rain . . .