The Mysterious Benedict Society, by Trenton Lee Stewart
Though this plot is being worn-out like an old cloth diaper, it still seems to work when done with a new, fresh spin.
Basic plot: Four children answer an advertisement that puts them through a series of tests. Then they are sent on a miraculous journey to stop a man from taking over the world. Filled with wordplay and arbitrarily labeled places and machines, this story is a clash between Charlie and the Chocolate Factory and The Gollywhopper Games, by Jody Feldman. The latter is a new release as of 2008 and the former I hope you've heard of.
Trenton Lee Stewart: