Jogging!! I go to the track and jog half a mile and my abs HURT the next day. Elipticals, walking, biking, jump roping.
Biking is good for exercise, I however dont do it as much because you have to do twice as much of it to get the exercise you would get with jogging. IM LAZY!! lol no but seriously it does work different muscles so it is a good workout but you are either going to have to do it for an hour to an hour and a half more so or jogging 45 mins.