Lose It!. It is a free website and free app for your iPhone. Just be sure to review your privacy settings when you first register. It has been a long time ago but it seemed like it was pretty open as default. I have since gone back and made my settings less restrictive. Having friends on the site is part of the inspiration.
Words of warning, don't try to be a hero and set your calorie goal super low. Just use what they suggest and modify after a few weeks. Slow and steady will win the race.
Want to be really inspired... go to their Forums... Fitness and Exercise... "Post your before and after pics", 3rd option down in the forum. Amazing photos that will totally blow you away. The other forums have great advice also but the pics are such great motivation.
Let me know if you join and I will send you a friend request. Just make sure your privacy settings allow me to request.