Downloadable Maps?

Does anyone know of an application that will run maps with GPS off-line? I am an avid hiker and can not utalize the maps with GPS feature wihtout a signal.
I have been using Tracks and MotionX (both paid versions). Tracks is great because its possible to download maps and waypoints from other users and sites but if I need an area that has not been uploaded..no map.
Mothin X is great but no signal no map.

Any advice on Applications? Is there a way to create my own maps for offline use?