As Glenny said tricep dips are great. Other exercise you can do easily are:
- push ups: start doing them on your knees and try to do them on your toes. Maybe add one on your toes each day.
- sit ups: you can do just the normal sit up plus do them on each side, leg lowers, side touches, ab prone/brace (google abdominal exercises and heaps come up with really good instructions)
- squats: do just the normal ones, go to the bottom of the squat and do small pulses, lean against a wall and do a squat hold
- lunges: do them with some cans of food in your hands to make them harder, hold on each side in the low position and again do the pulses
- squat jumps: these are awesome to get your heart rate up. Do jumps across the room and maybe do a push up and then jump back again.
- Bicep curls: fill some shopping bags with heavy things or use cans.
I hope alll that makes sense and gives you some ideas... sorry if I didn't explain the exercises very well! Good luck!