Nowadays I find chocolate and/or chocolate-based snacks to be great motivators. Everyone loves chocolate. If someone has a lot of work to do, put a piece of fudge in a glass container (so they can see it) and let them know that if they accomplish their tasks, they can eat the fudge. You'll definitely get a reaction!
Source: Business 2.0: How To Succceed: Avoid a Staff Mutiny (With Chocolate, if Necessary): http://money.cnn.com/popups/2006/biz2/howtosucceed/8.html
Contributed by: ~C4Chaos