The map that comes with the manual is useless. It's hard to decipher and it's not a direct screenshot from the real in-game map.
Color Hi-Detailed map and icons
http://www.fallout3nexus.com/downloads/file.php?id=1789
I've been using that one forever. It's a fairly detailed "satellite" view type map. The big downside is that it may break your sense of immersion as you become able to see every twist and turn of a highway. On the upside, for an experienced explorer, it's handy for trying to figure out which particular rock fall might lead to the top of the hill.