Installing Linux GUI's on Google Android phones
Ghostwalker at Android Fanatic has posted instructions for loading IceWM, LXDE, or other Linux desktop environments on Google Android. This requires installing a Debian Shell and a series of other utilities including an X server. It's not for the Linux newbies. Or for people who just want to use their phone the way Google intended.
In theory, you should be able to install GNOME or KDE following similar steps, but they'd probably be as slow as molasses on a phone like the T-Mobile G1. IceWM and LXDE have lower memory footprints and are designed to run on machines with slower processors.