So - what should you look for in a food journal?
1. fast and easy
3. free (of course)
4. mobile friendly
If the journal isn't easy to use - you won't use it.
If you are like me - you don't want to have one journal for food, another for fitness, another for habit tracking or sleep patterns, etc. Look for a comprehensive journal that lets you record a wide variety of activities.
As for mobile - this is obvious. I'm not a fan of 'apps' - simply because they have to be installed and updated. Instead I look for 'web apps' - basically mobile optimized websites that make it very easy to use from any mobile phone (android, iPhone, etc.)
Flexible just means that you can record a wide variety of types of information in the same system. The more flexible and more likely you are to use it.
My favorite free online food journal is LogsItAll.com - this site is free and, although targeted to athletes, is flexible enough to support a wide variety of activity recording (including food journaling). The calendar view makes it easy to see what you have been recording and the mobile site is fast and easy to use.
There is even a chrome extension that lets you quickly record details from within your chrome browser without even having to start a new tab.
Give it a try and let me know how you make out!