I am normally not much of a juice person - but I really like tomato juice when I am dieting. A big glass of tomato juice and some nuts or a piece of low-fat mozzarella cheese makes a nice lunch/snack. (And I can get large cans for 99 cents at the dollar store, too.)
Grab and go 100 calorie snack packs are great to have on hand for when you are hungry between meals. You don't need to spend a lot of money on prepackaged ones though. Larger packages of your favorite snacks can be broken down into 100 calorie packs. This is a page about 100 calorie snack packs.