Well, Davey Shafik started it with this post on his blog, and Firman Wandayandi (of DotGeek) continues it - a listing of "references on their desktop" - books/magazines/etc that are around them at all times for their reference.
What kind of reference materials do you use? What books are on your desk that never seem to collect dust because is seems like they're always in use? Do you have one of the giant PHP posters on your wall that SitePoint was offering? Post your comments below!