The Gumstix Overo is pretty awesome, with the Palo35 expansion board I am seriously reconsidering the purchase of a Nokia N900. The graphics look great and I can assure you that you will be seeing more of this board here.
If you are having trouble getting video working with a Gumstix Overo with a Palo35 with the 3.5" LCD touchscreen and you are searching for xorg.conf or something because the screen is mostly white and it looks like the modeline is wrong, hopefully I guessed your search terms.
While it is booting stop uboot and enter
setenv defaultdisplay lcd35
This will make the video work...