What little things through out the day can I do to get some exercise?

Alright, I've noticed that I have gained a little weight recently, and I want to get rid of it. What exercises can I do through out the day? I dont have time for an actual regimen, because I go straight from school to work, and from work to home to bed. I dont really eat much, but when I do, it's bad food like chips or something. What can I do through out the day to help me get some what of a work out?? Healthy food is kind of expensive, and I really dont want to drink/eat diet foods. So, at can I do?