Swimming. That's the all of it. Swimming is a complete body workout and it's low-impact. If your local YMCA or whatever offers a Masters Swim class (that just means we're geezers, not that we're Olympic-caliber swimmers) I highly recommend it.
My husband started swimming as part of his triathlon training and he lost something like 60 pounds in six months. I hate him, but now we are a triathlon family, he's in excellent shape and I'm starting my own training as a way to lose baby weight.
If swimming is out of the question, I also do Tae-Bo (Billy Blanks is a scary scary man but those workouts are TOUGH) and for Hanukkah I got DanceDance Revolution. Surprisingly enough, DDR is an awesome workout and even has a workout mode where you can track your progress.
Of course, eating habits and portion sizes are key to any weight loss effort, since it all ultimately boils down to math. Burn more calories than you ingest and you will lose weight. Just make sure your calories aren't entirely from Velveeta and you're halfway there.
The Addams Family Motto: We gladly devour those who would subdue us.