http://www.openstreetmap.org is a very cool project. Just discovered it for me, and spent the weekend with tracking and editing my hometown by car. Have a look here to see.
I am using SportsTracker for my Nokia E90 and JOSM for the editing at home.
Also checked for TrekBuddy on the phone to use a real moving map on the cellular. Maybe you want to use a little help for generating the map files for TrekBuddy?
Still much to learn, stay tuned for reports.
EDIT: Today (18th of June) at the LUG meeting in Mitterteich will be a short talk about OSM including some practices.