[rwh86]

Other than the ones that have been mentioned already, I also use Maverick, which has a free and a paid version.

https://play.google.com/store/apps/details?id=com.codesector...

I like its ability to show the different map layers, and it has great information screens that show things like GPS coordinates and such, great for geohashing or geocaching. Also has a cool display of how many satellites are visible and whether they're GPS or GLONASS or whatever.

The track recording feature is also nice, saving as a gpx file that can be easily uploaded to the openstreetmap online iD editor with drag-and-drop.