I use myfitnesspal.com & dailyburn.com
I have to track calories because I am a food addict. When I read that there is no need to count calories as long as you stay 80% primal my reaction is - oh boy, you don't know how much I can eat! I use fitday to plan my meals and stay close to my daily caloric needs.
The Spark People mobile app is really handy, though. And to be fair I've tried about five or six different calorie trackers and Spark is still my favorite, partly because the user-input food database is ginormous.
Also, it's waaaay easier to track calories on a Primal plan than a CW plan. 1) Fewer meals, 2) Fewer foods that are unlikely to be in the database, 3) You don't get carb-induced cravings and therefore don't have to spontaneously track five or six unplanned snacks. I'm also not weighing every single last thing I put in my mouth, I figure if I fudge up a bit here and there it's not the end of the world. Unlike CW calorie tracking, where when you ask someone, "Why isn't this working for me???" the first answer you get is, "Are you accurately tracking your calories? To the gram? OF EVERYTHING????"
I only track occasionally, and mostly for micronutrients, so I use nutritiondata.com, which only stores one day's results, but has a better tracking of micronutrients than any of the others I have seen.
A joyful heart is good medicine
He is no fool who gives what he cannot keep to gain what he cannot lose. - Jim Elliot
Mmmmm. Real food is good.
My Journal: http://www.marksdailyapple.com/forum/thread29685.html
I use LiveStrong.com when I do track, which isn't very often. They've got a really great iPhone app, which is a big deal for me. I usually will track a typical/random day once or twice a month to see what my macros are, and I also use it to chart my weight and get a better picture of what is going on.
Bit of shameless self-promotion here, but I wrote a blog post on the topic of tracking and obsession. Just my thoughts:
N=1 Optimization: Unhealthy Obession?
Oh my gosh! Thank you for this - paleotrack is amazing!!
I use sparkpeople.com but have changed my nutrition pie chart goals to 50% fat, 25% carbs, 25% protein. Its interesting... I'm eating about the same ammount of calories as i was, but I'm actually losing weight now!
I use the one associated with the BODYBUGG :: WELCOME because I have a bodybugg and subscription from CW weight loss efforts. I find it really useful to make sure I'm eating enough protein and to keep my carbs under control (or at least have a better handle on how many which foods have). I also find the calories burned part of the equation really interesting. I'm an engineer, and I love graphs, and this system creates some neat graphs.
This post has a great summary of calorie counting in the primal world.