From NachiWiki

It is required that at Least one wall switch-controlled lightning outlet shall be installed in every habitable room and bathroom of a dwelling unit. The exception that is important here is OTHER than Kitchens and Bathrooms a receptacle controlled by a wall switch can be used instead of a lighting outlet. (Excluding Hallways, Stairways, Attached Garages, Equipment Spaces and Storage Spaces and Outside Lights.

Also, just to clarify, other areas you MUST have a lighting outlet is Hallways, Stairways, attached garages and outdoor entrances.

Note: Nothing in the "code" says where the switch has to be located in the room. However, most electricans understand convience.

This article was originally based on a post by Paul Abernathy on the NACHI message board.