DrPetter, the talented developer behind Deflectorpool and Sfxr, just released an alpha for a new tool, called Sculptris. Sculptris lets you make 3d models quickly and intuitively as shown in the above video. You can export your creations as OBJ files or import OBJ files to use as a base for editing.
It’s really fun to play with. I made this ugly head after messing around for a bit.
This is an alpha, so the good Doctor recommends saving frequently, and reporting any bugs (or general inquiries) to him at the Sculptris forums. According to the readme, the final version is due in early 2010.