Those exercises do not require weights.
Squats and deadlifts, (1-legged to allow for the fact that there is no resistance)
Lunges, push-ups, pullups (don't need weight, just a bar or something to hang from)
Sit-ups, crunches, and a million other different variations of the sit-up and crunch, i.e. with a twist, legs up in the air, knees bent, legs straight, etc.