Mapper/GB is a Geographical Information System (GIS), with basic maps and systems of overlays which can be browsed around and searched. Importantly for use on a handheld, the use of vector overlays throughout (hardly a bitmap in sight) means that it's extremely frugal with your precious memory and disk space. A typical installation would be only a few hundred kilobytes, with a similar amount needed for the running program in RAM.
Mapper/GB is distributed in the freeware category and is 100% fully working, with *no* limits. Those wishing to donate a shareware registration fee can do so if they really like the program, using the info in the opening info screen.