Zach Even-Esh's
Real Man Fitness might fit the bill for you. It's mostly bodyweight stuff, with tips on adding in a few more things to your workout arsenal. He suggests one dumbbell. Just one, so you can basically just keep it in the corner or under your bed. One db is cheap, too. Either the adjustable one or one decent sized solid db.
It's simple, basic stuff, but it might be perfect for someone who's busy and doesn't want to or can't get to a gym.