Nowadays, I am trying to stick to three meals, but sometimes I work in a LC snack between lunch & dinner or possibly late in the day if I eat dinner too early. Some things I eat that haven't been mentioned yet:

Grape tomatoes
Melon chunks
Miso soup
Can of light soup
Marinated mushrooms
Marinated roasted red peppers
Defrosted cooked shrimp with homemade "cocktail" sauce (salsa + hot sauce)
Any leftover cooked veggies
Cucumber slices w/LF dip/dressing

I try not to get any significant amount of calories through my snacks - for me they're purely a mental health thing. :)

It's usually raw veggies (celery, carrots, bell peppers, broccoli, cucumber, tomato [ok, that's a fruit]) or fermented veggies (sauerkraut, pickles, kimchee, pickled ginger carrots).

Baked/dried edamame beans, olives, cherry tomatoes or a handful of almonds tend to be my snack of choice.