Although "time" is a difficult one within the context of "best things are for free", I think it fits in somewhere.
Certain people might argue that time is money. My theory of the day says: Don't be fooled - this is only true because of the measurable work you can do in a certain amount of seconds, minutes and hours. Not because of the time itself. Time exists with or without us. It's a handy, free tool.
So, if you do nothing (like me today - see above) or if your work is not measurable (like mine today) time is just happening. Completely free. And why is it so good?
Because you can always say: "Remember that time in Toscane under the moon and stars, when you were supposed to do something romantic but fell of that small stone wall, and landed wih your bum in a bed of peppermint plants?"
In the end it slips through our fingers anyway.
Free time for all!