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pushups and situps can potentiall do more harm than good.
A pushup puts unnatural stress on the back and shoulders, while a situp puts stress on the shoulders and neck.

www.sparkpeople.com has a great list of exercises.
You also might want to look into a core workout, like pilates.
You need to incorporate cardio and weight-training into your routine as well, if you want to really do it right.

Cardio you need to be doing atleast a half hour a day, vigorously enough to get your heart-rate into it's target range.

A great exercise I do in my room are body builders. It's kind of like a burpie, if you know what those are.
You start standing up, than drop down to a squating position (your hands should be on the floor.) Pump your legs out behind you into a push up position. Although Groovy did say push ups put unnatural stress on your back/shoulders, you have the option to do a push up here. If you chose not to, pump your legs back to the squat position with your hands still on the floor. Than in a fluid movement, jump up into the air, stretch your arm up to the ceiling. Once you land, that's one. You can do as many as you like, I usually do around 20. =)