I know what you are talking about! It took me two years and 3 months after my daughter was born to start losing weight. I finally implemented what I call my Healthy Eating Plan. It's a set of rules I follow that are rather strict, but that really work for me. Exercise is good, but it often lulls us into thinking we can eat what we want. I find changing what I eat most effective.
For accountability I started to blog about wanting to lose weight and described my plan. Once a week I tell how much I am weighing. So any random stranger that comes upon my blog can read rather personal information about me. That is a GREAT deterrent for me!
I describe my plan here: http://shoozieshoes.blogspot.com/2008/12/healthy-eating-p...
I am by no means a professional, so take it for what it is - something that has worked for me. ;-)
Best wishes with your own plan!