Same as DBE, I give it to the pigs - its their absolute favourite treat, they love it!
Alternatively, if I'm feeling enthusiastic, I make ricotta and then give what's left after that to the pigs.
Easy ricotta: leave the whey to stand for 24hrs to acidify further, bring to boil - the ricotta should appear in the whey as cloudy white bits, then filter - this bit takes ages as the fine ricotta completely clogs up the filter/cheese cloth and is the main reason why I so rarely bother!