Skyrim hasn't even been out for a week yet, and we are already seeing some mods for it. One worth noting isn't really even a mod, but it changes the way that you view the map in game.
The map in Skyrim is an actual 3D version of the game world, and if you add a few lines to an .ini file, you can zoom in all the way, and move around the world. This is actually amazing, and it lets you see and find things ridiculously easy.
Complete directions on how to do this can be found on Skyrim Nexus.
Skyrim map mod provides in-game street views [PC Gamer]