The 6 in. veggie sandwich at Subway is great and low cal. If you get everything on it (including cheese, minus oil) you don't miss the meat. Plus I believe it's one of the cheapest things on the menu.
Other than that, the Happy Meal at McDonalds isn't too terrible. Just keep to plain hamburger, and diet coke.
Good luck! You'll be surprised at how seemingly small changes in your diet will add up.