The number one thing that has helped me develop a healthier lifestyle regarding eating and exercise has been having a place to track my calories in and out. The best website I have found for this is SparkPeople. SparkPeople provides a wealth of information including access to articles, exercise how-to's and short exercises videos, recipes, nutrition calculators, fitness calculators and provides a social networking aspect similar to Facebook. When you join, you can create your own page reminiscent of MySpace where you can add pictures (such as before/after, progress, etc), update your status ("Just got back from Zumba!"), blog, and receive comments. Also, SP has teams you can join to meet people with similar goals or interests, competitions, and message boards.
I mainly use this site to track my calories in and out and to give and receive support from other members. I have made some friends on SP, and that support really helps keep me motivated.
What keeps you motivated?