I love love love myfitnesspal and track it everyday. I have found lots of friends on there so you can comment on their status, exercise or food for the day which is really motivating!

I also recently found the fitocracy app which is somewhat a competition for your workouts. You earn points for tracking workouts and can level up. There are so many groups on there to get a lot of good information. People can give you props on your workouts or posts and everyone is so motivational and encouraging! It's a really cool app.