I hate to admit it but when I am crunched on time and need something fast I pick up Jack In The Box's Tacos for lunch. Not the healthiest by any means but it sticks with me, has less than 500 calories for a meal and only costs around $3.
2 Tacos (408 calorie)
1 Side Salad (20 calories)
Low-fat Vinaigrette Dressing (40 calories for the whole thing- I only use like a quarter of it)
Diet Soda (0 calorie)
Oh and the Jack In The Box out here now has the freestyle machine. Which is AWESOME! So many diet choices I love it!