I'm a very light person, and have quite a lot of energy. Since I don't have much weight to push up (I'm 150lbs and 6 feet tall) I can do quite a few.
I am quite agile and mobile most of the time (summer mostly) but I did 75 before lowering, breathing, and then stretching. I'm going for 100, but not yet =/
so to get there, I do 75 (less sometimes depending on how my day was) and then I do a second set to get to 100. I usually stretch out my legs and do sit ups as well. (100 of those)
I don't have a weight set (or at least one inside. We have one outside in our garage, which I made a new years resolution to use once it gets warmer... since it's fuckin COLD in Ohio...) so jogging works well. I also recommend climbing trees. Great excercise (pulling yourself up, balance, stretching for branches, etc) and it's fun to get higher up ^^