Dan Ariely recently spoke at the Commonwealth Club of California on "The Hidden Logic that Shapes Our Motivations." He covers a lot of ground in psychology and behavioral economics, but what really makes it worth listening to is the discussion of what motivates employees to work hard and do a good job.
There's probably as much practical management wisdom packed into this one hour podcast as in an entire shelf of management books. It's worth listening to the whole thing just to hear why you probably shouldn't pay bonuses to your best employees. Along the way you'll also learn that pizza is sometimes better than cash, and that incentives can cause productivity to decrease.