The world’s two worst variable names is a good article based on Steve McConnell’s excellent book Code Complete:

Variable naming conventions can often turn into a religious war, but I’m entirely confident when I declare The World’s Worst Variable Name to be: $data
Of course it’s data! That’s what variables contain! That’s all they ever can contain. It’s like you’re packing up your belongings to move to a new house, and on the side of the box you write, in big black marker, “matter.”

(via Small Values of Cool)