[GeeTwo]

While it was not intended this way, we trained two rookies this year using our air cannon. The arduino control system (or more precisely the xBee communications modules) were not working, so two veterans and two rookies built a control board to drive our air cannon using FRC competition electronics between successive football games this season. As long as you don't mind taking an old project apart, and not having the current project stick around more than a few weeks, this does not need to be expensive; mostly wire, terminals, tie-wraps, and possibly a fresh board.

Edit: as far as useful to the team, it depends on your needs. We have done a few lighting projects (including solar) over the years, and done minor repairs to non-competition electrical items (with a mentor to double-check the work).