1. Lose the pegs.
2. Hack off the bottom section of your seatpost (if you don't intend to raise it again).
3. Slime-tubes rock, but when trying to save weight, stay away from 'em.
4. If you're desperate, take off the brakes and use the good ol' foot-on-the-the-back-tire.
5. Ditch any reflectors you have, but not if you plan to go street riding in the middle of the night.