Software:
- The preinstalled "Maps" application.
- Maemo Mapper - you can download Google Earth / Virtual Earth maps and aerial photos from within Maemo Mapper.

These are the only useful GPS related N8x0 applications which I'm aware of. Well, in addition there is Kismet (wireless scanner), which can also use GPS to show the exact location of the wireless networks it detects. Unfortunately at the moment Kismet is not very usable on the N8x0.

Bluetooth GPS receivers:
First I had the Nokia LD-3W, which I sold recently to to replace it with a Nokia LD-4W. Both are working together with the N800 like a charm. Connecting these GPS receivers to the N800 is very easy and both have an equally good GPS performance (Sirfstar III chipset). The LD-4W is smaller and more lightweight than the LD-3W, but also more expensive.
http://img183.imageshack.us/img183/4...tures11fw8.jpg