At Team 2345, we used two window motors that run a 8'' diameter "sticky" wheel with a deep groove cut into it to facilitate the orange cord you see in the video. The cord then runs to several 4'' diameter pulleys
http://www.youtube.com/watch?v=IE9j5TSII7M
(If the link doesnt work go to youtube and type in "FIRST Team 2345" video is under "FIRST Team 2345 KARS 2012 Ball Converyor Test")