My favorite mega-filling low low low calorie snack is bean sprouts that I sprout myself weekly.
You can use the regular beans from the grocery store or order them online (garbonzo/chickpeas, peas, lentils, mung beans, adzuki beans). I use an empty pickle jar, a piece of netting and a rubber band as my sprouting vessel (no need to spend money on fancy contraptions they advertise online). Here is a very down to earth, no-nonsense intstructable on sprouting
http://www.instructables.com/id/Spro...r-own-Sprouts/
I actually like to eat these at about the 3rd day when they are still bean shaped and just starting to sprout. They are crunchy and more of a snack of a vegetable then a salad item (I really don't like salad...).
Usually I eat them plain by the handful. Sometimes I'll dice up tomato and cucumber and make a greek dressing. Or just lemon, salt and pepper.
An entire CUP of sprouted mung beans is only 15 calories. If you ate a whole cup though, you would feel like you were gonna burst. Lentils are a but higher at 82 calories for a cup.