The VoxelMap is a very nifty minimap that displays elevation, terrain, mobs, and other players (in multiplayer)! It also has an enlarged mode, a square mode, and a zoom mode!
You can change the map’s settings easily through it’s custom settings panel (press m).
The mod also has waypoint support, and automatically tags your last place of death, so don’t worry anymore about not being able to find where you died.