I've reviewed several products lately, some free, some not, and thought I'd share my thoughts about some of them. We'll start with the totally free :)
The Lose It app for the iphone/ipod touch is a completely free program that helps you keep on track for weight loss or maintenance. I've spoken about food diaries before, they are one of the best tools for assessing and tracking your progress, and I've rarely seen any long-term success without them.
The Lose It app has a robust database of pre-programmed foods and the ability to add your own custom foods and recipes. There's also a database of exercises so that you can log in your activity level. You will enter in your current and goal weight and how fast you want to lose and it will give you a calorie budget for the day. Logging your food and exercise will automatically update your budget in real time and allow you to see how much more you can still eat that day and stay on track. There are daily and weekly reports, which can be emailed to you, with lots of pretty graphs if you like that sort of thing (I do, especially when they go the direction I want them to). A friend feature allows you to add friends to help with motivation and accountability.
The only downside I see to this program is that it does require an iphone or ipod touch as there's no current ability to use the web to enter the data. The web will allow you to view the reports and there's a forum group where you can connect with other users for motivation and support.
If you have an iphone or ipod touch, give this program a try...it's totally free and not a trial version either.