Freakonomics was a great book, loved it ( I have the one with the apple/orange cover, it's nicer than the other one :) )

If you liked Freakonomics and The Earth is Flat, you'll also like these Books:

Malcolm Gladwell's Blink and The Tipping Point, Naked Economics by Charles Wheelan, The Long Tail by Chris Anderson,
The 4-Hour Workweek by Timothy Ferriss, Crossing the Chasm by Geoffrey A. Moore, Fish! by Stephen Lundin, Trust us we're experts by Sheldon Rampton and John Stauber.