Tim Ash has a look at creating Normal Maps in Maya using the Turtle Render Engine. Turtle Render comes with the Maya install as a sophisticated baking plugin used for lighting and content creation in next-gen gave dev.
How to bake Normal maps using the Turtle renderer in Maya.
The Turtle Render engine can easily bake GI solutions into vertex maps, texture maps or point clouds. The engine also makes short work of baking occlusion and normal maps from high polygon models to low polygon models.