Making cheese is the obvious answer, but needs more or less a whole day set aside to do a couple of batches. However things like Feta or even just soft cheese are quick and easy. Feta can be preserved in olive oil for quite a while, and you can freeze the soft cheese - less in volume terms than milk would be!
A cream separator and then ice cream is what we do a lot of, but I am waiting until our pigs arrive later this autumn to have an outlet for the skimmed milk.