I have been meaning to write these out for a while, but here are a few off the top of my head:

Light soy or almond milk is fewer calories than dairy milk.

If you want a warm beverage, a hot cup of chai tea (the tea bag kind) or good earth original spiced tea with a splash of milk is good, or low calorie/sugar free hot chocolate added to nonfat milk.

Nonfat Greek yogurt + dry ranch packet = fake ranch that tastes almost like the real thing. And trader joes makes a guacamole that uses Greek yogurt to lower calories.

A can of campbells vegetarian vegetable noodle soup is like 200 calories and very filling. Or add hot water to a bullion cube and curry powder from the packet (sold at asian groceries) to make a spicy broth that is ~30 cals.

Just need a carb vehicle? Go for pita bread, sandwich thins, bagel thins, low calorie wheat wraps, and rice cakes.

Replace steamed rice with cauliflower that has been grated. This works especially well with spicy foods like curries.

Egg whites in the carton are easy to add to stuff. You can make a super low calorie and tasty pancake by mashing up banana and egg and a bit of flour, then putting it on the grill.

Use mustard and light/whipped cream cheese instead of mayo in egg salad.

Laughing cow makes light cheese wedges that are really good for replacing many spreads.

Chicken muffins. Google them.

Trader joes makes low calorie shredded mozzarella that is half the calories of regular and I can't tell the difference. I put it on a low carb wrap in the oven with turkey pepperoni to make mini pizzas for 100 cals each.

For dessert, 90 calorie tofu ice cream sandwiches rule. As do 40 calorie fudgsicles. Add hot chocolate powder or low calorie pudding mix to nonfat yogurt. Or take a frozen banana and blend with milk to make fake "frozen yogurt". Meringues or angel food cake are also pretty light on calories, relatively speaking.

Apples. Watermelon. Most fruits taste way better than their calorie count IMO.

Pickles!