Every once and a while, a website comes along that changes the way the you go about your daily life. Gmail, Facebook, Twitter just to name a few. myfitnesspal found it's way into my daily routine very easily. One stumbling block of keeping a food diary has always been knowing how many calories something is, what the serving size is, and keeping the information in a way that is useful and convenient. myfitnesspal does all that. At it's core is the food diary. You define up to 6 'meals' a day that you want to track and when you eat something you choose a meal and click add. A quick search of the very large database and generally you can find what you are looking for. If not, you can always just quick add calories if you have a guess. The site has good mobile apps that really make it easy to use. A barcode scanner in the mobile apps lets you enter packaged food by scanning it's barcode, it rarely cannot find what I'm looking for. MFP then helps you keep track of calorie intake. It also hooks up to several fitness apps like Endomondo, Runtastic, Fitbit and others to help you keep track of burned calories. The site lets you track measurements for weight and body size (or any arbitrary numeric measurement). There is then some basic reporting features on this data. That is probably one of the areas the site needs the most work, but it does seem pretty new still. The site has some social features and an active user forum, best of all, it's free.
I would highly recommend that if you are wanting to do a food diary, to check out myfitnesspal, it has helped me stay focused on my goals for over 80 days now and still going strong.