Especially in the winter - I present to you the idea of Lipton's Cup a Soup as a snack. They are all under 100 calories - some just barely - and others like the Spring Vegetable - are only +/- 50 calories. For these I add one Ak-Mak cracker with one tablespoon of hummus.
Eating this snack *feels* like eating a meal - it is wonderful...
Hmm... I've got this down to a science. I go for what fills me up and holds me for 3 hours.
Tuna. If you can eat 100 calories of tuna, you will have problems eating at the next meal time!
I love soup and could live on it... Most Progresso soups (regular food, not the diet version!) are less than 100 calories a serving and really keep hunger at bay.
Campbells has some good soup options, too. Several are less than 100 calories so you can add crackers.
For snacks when you aren't hungry:
Healthy Choice Fudgecicles are 80 calories and they taste the best... I've tried all of the diet desserts.
Individual fruit cups are good, too! The Dole mandarin orange slices are great as a snack and on salads. I use the juice in place of salad dressing!
Have you tried those packages of pre-grilled sliced chicken strips that are by the lunch meat at your grocery store? I discovered them a few years ago and they make good protein snacks and/or quick salads... and I don't have to cook them! Same with pre-cooked bacon.
Soup is very filling! There is a lot of sodium in it, though. Just drink the water too (easier said than done)! In any case, with soup and water rolling in your tummy you will be full!