Powered by Windows Live Local, Windows Earth Mobile lets you get maps on your WM5 devices. Normally, Google Maps and the like don't work very well with pocket IE or Opera Mobile, but using this, you can see regular street views, satellite views, or a combination of the two. You can even use this for driving directions after setting two way-points as your start and finish.
Personally I have a GPS nav system in my car, but when I'm riding in anyone else's car, it's nice to know I can access maps and directions from my phone. Works on WM5 and Windows Mobile 2003.