The ball is good for a few things, especially crunches. I don't have any exercises for resistance bands but you might be able to find something online, try searching through google.
A good inner thigh exercise can be done with the ball. If you lay on the floor and put the ball between your thighs, squeeze for 5 seconds or longer, then relax. Repeat.
There is a similar hamstring exercise you can do with the ball. Lay on the floor, and put your heels on the ball and then press into the ball with your heels lifting your butt slightly off the floor, hold that for 5 seconds or so, then relax.
Squats can be done with the ball if you put the ball between you and the wall with your feet out as far as possible (Make sure that your feet aren't under your knees). Then lower your body as far as possible then return to your original position.
You could also do pushups on the floor or with the help of the ball.
Your options are probably limited without weights but these are some things you can do. Definitely read over the stuptuous website, it is a good resource.
You can't out-exercise poor eating habits.