I remember doing these wods as warmups. Now they are called calisthenics. (confession: I watched a lot of calisthenics videos last night and now feel inspired to do something about my fucking flabby-ass core.)
The purpose is to go:
(Level 1) 20 seconds on, 10 seconds off....
(Level 2) 30-seconds on. 15 seconds off....
(Level 3) 1 min on. 30 seconds off. (or no rest in between... try it out. see what you're comfortable with.)
Pick 5 of the following and do them now! (no excuses!!!)
plank
super-mans
flutter-kicks
L-sit on a bar
"windshield wipers" (where you lay flat, hold a broomstick above your head. bring your straight legs up and touch the ends of the broom stick and the center. repeat.)
navy-seals (basically, a lot of "up-dog/cobra" in yoga moves... but without touching the floor.)
front/back leg kicks (balancing on 1 leg, kick in front of you then kick behind you. don't have the kicking leg touch the ground. Rinse/repeat for the opposite leg)
side plank (L/R)
Hand-stand hold
ring-dips (or just dips off any object)
mountain climbers
Situps with your legs up (v-sit crunches)
pullups (modified any way you can. Eventually you want to do strict.)
pushups (modified any way you can. eventually you want to do diamonds.)
I'm sure there are more... but this is all I got for now.
just 5 minutes.