Tube, patch kit, levers, CO2 cartridge, cell phone, ID, chapstick, snack of some sort. I just don't like the feel of stuff in the back of my jersey (unless I'm commuting through the ghetto...then I keep my cell in my jersey pocket).
A girlfriend of mine just carries a cell phone. I feel a bit unprepared with just that.
2007 Trek 5000
2009 Jamis Coda
1972 Schwinn Suburban
"I rejoice every time I see a woman ride by on a bike. It gives her a feeling of self-reliance and independence the moment she takes her seat; and away she goes, the picture of untrammelled womanhood."
Susan B. Anthony, 1896