Two words: Breco flex. There Belts are amazing a little expensive but you can't beat them. Another thing I would like to add if you doing a belt drive spend the money on good belts it's worth it trust me, Bad belts are the worst thing. Breco Flex has many models of belts that you can chose from.
www.Breco Flex .com
My Team 1251 used belts not breco flex but we got a pretty good system going so check our bot out.
http://www.chiefdelphi.com/forums/sh...techtigers+bot
My two cents,
-Drew
1251 The Tech Tigers
"We even bleed Orange"