It takes a lot of supplies to pack 1,100 backpacks and your donation can go a long way.  Operation Backpack needs kid-friendly supplies, the kind of things you would take in a camping backpack,* including:

Canned Goods (ravioli, tuna fish, Vienna sausages, etc.)
juice boxes
individually wrapped cookies and crackers
cereal and granola bars
packaged snacks
dried fruit
school supplies (pencils, crayons, paper, etc.)
miniature toiletries (hotel sized)
Bottled Water