I saw the post below about Google Maps for the WM Treo, and I thought I should point out that Google Maps has been available for a while for the Palm OS version of the Treo. It is running like a charm on my 680. Here's a screenshot of my town.
The program can also show satellite maps. Here is a map of the same area as in the shot above.
You can get Google Maps for your Treo at this address. Just go there with the Treo's web browser and download it directly to your phone.