I did my warmup on the treadmill, hit the weight plan I'm developing (thanks April for the women's weightlifting site), then went back on the treadmill for 45 minutes for a total of 3 miles. Ended the workout with abdominal crunches and an abdominal exercise I learned on from a Pilates video.
DisBo-you can do the treadmill everyday, but I would say out of a week take a day off or just do a 30 minute walk. Your body will do better with rest. I was doing it every day, and missed one and was very upset until I saw how much better I did on one day's rest. Like gshoe said, go by how you feel. If you are tired, don't push. When you get stronger, try interval training, which mixes up walking and jogging, and/or increasing and decreasing the incline. It makes your body burn the calories differently because you are challenged in a different way than the regular routine. I am doing this now hoping it will knock me out of my plateau.
Good Luck!
Kathy