yogurt - Fat Free, or Low Fat, Plain - add your own fresh fruit
Toast and jam - Like valias said, choose smartly - sprouted grain bread over any other kind, and low sugar or sugar free jam, OR you can use hummus instead. That's delicious. If you've never tried it, I suggest you go out and get some or
try to make your own - not too hard to do with a blender or food processor.
Slice of cheese - By itself? Hardly a nutritious or fulfilling snack. Pair it up with some fruit, or cook it up with some egg whites in a nice little omelette. Stick with fat free or low-fat cheeses.
Bowl of fruit - Pair it up with yogurt or some cottage cheese (fat free or low fat)
Veggies - can be a great thing, from salads, to sides, to veggie omelettes (i love omelettes, can you tell?), and even some veggies with fat free cheese or with yogurt or cottage cheese for "dipping"
Nuts - not a good idea as a snack all by themselves, unless you can metabolically afford to eat a ridiculous amount of calories a day. A small handful of nuts can easily pack in 200-250 calories or more depending on the size of your hand. Pair up a serving of nuts with some yogurt, or a fruit, or toss some nuts in a salad or in your rice, but don't count on nuts as ONE SNACK on their own. You'll surely overeat.
Frozen yogurt - tough one. You can make your own in an ice cream maker, but I'd reserve this for a treat/cheat or PWO if your diet and goals afford you that luxury.
Bowl of raisin bran - not bad, with some fat free milk or fat free yogurt. Be careful with these, because the typical mainstream brands have sugar-coated raisins and such. Just read the ingredients and stick to the brands that have the least number of ingredients, or the most BASIC ingredients (easy to pronounce, usually hahaha).
Other snack ideas
Beef or TUrkey Jerky
Cans of Tuna (low sodium, packed in water)
Cans of Salmon (same)
Cans of Chicken
You can pair these up with a slice or two of sprouted grain bread or mix them up with the appropriate serving size for your diet of EFA Mayonnaise, or Olive Oil Mayonnaise. Spectrum brand has some healthy mayonnaise options.
You can also mix them up with hummus.
You can ALSO eat your veggies with the hummus.
Cottage Cheese singles - I know breakstones sells little snack-sized containers of fat free cottage cheese.
You can add a tbsp of peanut butter, nuts, dried fruit, cereal/granola to the cottage cheese.
*Though I don't think you shoudl rely on these things - shakes and decent-sized meal replacement or protein bars (not the 500-cal monsters, with tons of crap in them).