A lot of times I will make a sandwich for lunch and eat 1/2 with some fruit or veggies and save the other half as a snack.
Other ideas:
Small baked potato w/cottage cheese
1/2 PB sandwich on whole grain bread
Celery sticks filled with peanut butter
Cup of homemade trail mix: nuts, dried cereal, dried fruit
Cup of soup w/whole grain crackers
Small bowl of beans and rice
Small salad
Cheese and whole grain crackers
Homemade whole grain fruit-nut muffins
1/2 banana wrapped in taco-size whole wheat tortilla w/PB
tuna salad w/whole grain crackers (about 1/2 can?)
Boca patty
Smoothie
Veggies w/plain yogurt dip (season however you like: ranch dressing, hot sauce, salsa, salt & pepper, lemon, etc...