Four Way Rubber Bands
Scottsdale, AZ based Flying Buffalo makes these 4-way rubber bands, called Box Bands, specifically to hold board game boxes together. Clearly they'd be great for stacks of paper, books or anything else you'd otherwise wrap with twine or multiple rubber bands. They're available in 4, 8 or 10 inch sizes for $5 per pack. You can buy them directly from Flying Buffalo.