This is a bit of a gimmick but it's rather fun.
I got a Blackberry 8310 Curve from work a few weeks ago and the new model now comes with a built in GPS receiver at no extra cost.
It works OK with the built in Blackberry Maps, but it tends to be very American centric and not the easiest to use. So I did the usual google look around and found the following.
Google Maps - Mobile version - A simple download and install onto the device, talks to the GPS receiver automatically and give you accurate (usually to 3 meters) location data with Map or Satellite imagery and it locks onto the satellites very quickly (a lot quicker than my really crappy Garmin c510 satnav).
The I found this application called BBtracker, it's an open source project that stores data from the GPS, does a few calculations and will then show you a real time plot or your direction, distance, speed and elevation. All plotted over time.
It's not a very pretty application. But it does allow you to export the data in 2 formats, one of those formats is for Google Earth.
I set mine up to track me every 3 seconds and did a drive from home to work. It plotted me exactly on the road from start to finish.
It very simple to do to, I tell BBtracker to export in the required format onto the SD card on the Blackerry, then I connect the Blackberry to my PC via USB, open Google Earth and open the exported file and import it into Google Earth.