Have you tried Soy yoghurts? My son loves them!
We have lots of fruit for snacks - any that he can feed himself, rice crackers, wine biscuits (that's what they're called in NZ, like rich tea), cooked carrot sticks, scotch pancakes, little sandwiches with marmite or cream cheese, toast...
Even tried Jelly which he quite liked playing with, but not keen on all the sugar in it!