[Michael Hill]

Pneumatics is something extremely valuable to learn in the off season. It opens up a whole new world of linear motions your robot can have. I would hold off on drivetrains for now. For the past few years, the kitbots have been pretty darn good and can shave a week or two off of your build schedule allowing you to concentrate on game piece manipulations. The GDC tests each game with the kitbot to make sure teams who use it will at least be able to play the game. You might also check out the Vex Drive in a Day stuff as well as 1114's Kitbot on Steroids (though it might be somewhat outdated). All of these drive systems are very well developed by people who really know what they're doing.

Other things you can do to help out in the development of your team are learning CAD, having machine tool training, safety training, hand tool training, etc. As you mentioned in the OP, I would recommend learning how to use sensors as well. I would start with the sensors that are used most often, then work your way down. That is, I would probably start off with learning encoders (grayhill or U.S. Digital), then work with gyros and accelerometers, then you can work on stuff like Reed sensors for pneumatics, limit switches, and potentiometers. Encoders are very useful for driving autonomous mode and things like arm positions. Gyros and accerometers can be coupled with encoders to help out with determining position and orientation for things like autonomous mode (and I believe straight drive?). Reed sensors allow you to pick up the status of special pneumatics with magnets on the pistons. Limit switches generally consist of a lever bar pressing a button. They're not used as much anymore as they used to, but can be an extra level of protection so an arm doesn't collide with your robot. They usually work...usually. Potentiometers can be used as rheostats. Basically, they're a variable resistor that will change the voltage (through Ohm's Law) with respect to a change in position (either linear or rotary, depending on the pot). They can sometimes be used instead of encoders, but unlike encoders, they can't go an infinite number of turns (most can't go more than 1 rotation) and they're also, generally, not very linear (that is, change in voltage/change in position isn't always constant).