I second the stairs if you have them. Awesome workout! Just be careful as it packs a mega delayed onset muscle soreness. I shredded my legs a few years ago and was barely able to walk for a week. LOL! I'm more careful about it now. I run up and down the stairs for three minutes, then do 20 squats then a 2-3 minute wall sit. Repeat for three sets.
If you want to add some strength, which I highly recommend, this is the perfect time to do it! You can do push ups followed by jumping jacks to get the heart rate up and alternate for three sets.
Dips using a sturdy chair.
Invest in 5, 8 and 10 pound weights (not terribly expensive and you could start with just 5's) or use canned foods or jarred foods to do bicep curls, tricep exercises, etc.
Maybe purchase an exercise ball? That's the last "but-it" I'll suggest.
There's just so much you can do at home with an exercise ball and a few weights.