If you're ever in Pullman, Washington, stop in at the WSU dairy store and get a few cans of Cougar Gold cheddar. Cheese in a can sounds weird, but it's delicious, made by the students, and it ages really well -- I've got some cans in my fridge which are coming up on a decade old now. It's kind of a waste to use an aged can for mac and cheese, but I used part of a younger can for mac & cheese and it came out beautifully.