Could pick up a cheap Core2, flash to 2,1, install 4gb DDR2 (it'll only use 3gb), and get an SSD in there.
Install Windows 7 (32bit) on it. OSX is a misery to use on them, and can't officially go past Snow Leopard.
It's not really worth the effort...
I still like them, but that Intel 945 is just doom.