It's pump, multi-tool, spare tube, levers for me. Ditto on the spoke-breaking. Our tandem has only a 36-spoke rear (prob. replaced by prev. owner), and we bust a spoke once or twice a year. I loosen the opposing spokes a bit to pseudo-true the wheel, and back off the brake, and we're fine 'til we get home.
Another bit I read somewhere else on these forums: cut a 3"x3" or so piece of tyvek from an envelope and throw it in your bag. If you have a tire problem, it might keep the tube from herniating through it, at least under low-medium pressure.
If you carry a cell phone, another thing you might want to carry is a Better World Club card. They're a competitor to AAA, with two major differences: (1) they aren't lobbyists for the roadbuilders and auto industry, as AAA is, and (2) for about the same price, you can also get bike breakdown protection.
Oh, and some bus tokens.