OziExplorer has been a longtime reference for off-road navigation, with its PC version, then its PocketPC/Windows Mobile version and now Des is porting it to Android with BetaOzi already available for testing. It's quite limited though so in the meantime we can use Androzic that has a full set of features, on the fly route creation, follow route, etc...
You can create maps with Mobile Atlas Creator in the Ozi Explorer format and then convert them to the mobile ozi format (ozf3) using img2ozf utility (no later than v3.03 as the ozf3 format was changed after that).