Well that's how I wanted to do them, but at the moment the equal-level ones are working fine. Also because I don't do normal push-ups, but the ones Goldmember recommended (with the elbows close to the body).
At the moment I'm only able to do 13 of them, but when I started last Monday it were only 11 so it's going upwards.
With one-hand-push-ups I'm waiting till I'm able to do 10 or 20 handstand-push-ups (with the back against the wall). Sounds curios but I once read it's a good workout and I'll probably give it a try one day.
Well, actually I'm doing the following everyday (okay, six days a week):
Equal-level-push-ups: till I can't do more
Sit-ups (rec. by Rude_God): till the belly hurts too much
Chin-ups: till I can't do more (poor 5 at the moment, but 2 more than last Monday)
1-&-2-legged-knee-bends: till I can't do more (didn't count, but I do them like the sit-ups, staying down in the squat, like skiers when they are going downhill, until the thighs start burning)
As you can see this is a very modest program, so I would be thankful if anyone could tell me some more bodyweight-exercises.