Anyone know of any good exercises that don't use weights or machines?
Is it that you don't have any weights? Or you're actively choosing not to use weights? Just wondering.
Just know that using strictly bodyweight movements will get old pretty quick. Once you can handle more than 10 reps or so, you're not building any appreciable strength or size. So, it depends a lot on your goals.
Here's an article by Mike Mahler, about some classic, though controversial, bodyweight exercises:
Here's a great interview with Coach Sommer, discussing gymnastic moves (always a great addition to bodyweight routines):
Here's one by Thibideau, which may or may not be useful, depending on the equipment you have available:
One-arm: push-ups, pull-ups
Handstand push-ups, Sternum chin-ups...are a few.
I think someone named Bryce Lane had a site which listed a whole bunch of this kind of exercises and variants. I don't know his website, but you could search.
You can do ALL these with bodyweight only. You get even greater benefit if you can indeed add some weight (dumbbell, barbell, bag of sand - anything really):
Pull-ups, Push-ups, dips (using a chair if you don't have dip bars), lunges, squats, romanian deadlifts, hand-stand push-ups, V-sit-ups, crunches (lots of ab work, in fact), one-leg calf raises, one-leg squats, and probably a ton of others. USeful for when you're in a hoel room on travel and there is no gymn (not even the usual piss-poor one) to go play in.