Here is a bodyweight workout from Coach Stacey. You don't need ANY equipment. Your body will offer you plenty resistance to do the following:
FULL BODY: 10 rounds of 10 reps each
ABS: 4 rounds x 30 sec NO BREAK
Mtn climbers and lunges are per leg (10 pairs).
Start the timer. Next time you do it, try to beat your time!