M.P.
Before I got pregnant I had great success with the Six Week Body Makeover and at $100 it is not bad!! The only thing is they suggest not doing it while you are breastfeeding, so if you are you might want to wait because it is a pretty strict diet - and that is what I needed to keep me on track!!
I also joined Babyfit.com. There you can find other moms who are in similar situations. They send you daily exercises, recipes and food for thought if you want and you can view message boards and chat with other moms (it is set up similar to myspace). I find it really helpful to have a small group of women to keep myself accountable. Hope that helps!