Not sure if this idea has been said yet, but I thought it might work to have a setup similar to the Team 2648 Breakaway bot (
http://www.team2648.com/our-robots.html). If you have two of the arms shown on each end of the robot, it would be fairly easy to have one attach to the first level, lift the robot off the ground, and then have the second arm on the back attach to level 2. I don't think it would be feasible for it to reach level 3, but I thought it was a decent plan.
A problem with this, however, is that the first level is only 30 inches off the ground, which might make it difficult to accomplish the lifting mechanism shown.
Any ideas on this?