I read this novel series where the currency of the society was energy or its equivalent in computer cycles or time. That was an interesting take on how currency could develop in the future.
Speaking of currency, I'm wondering if I should consider converting my assets to euro, it being stronger than dollars and it's poised to possibly become the world's reserve currency.
There was a science fiction story some years ago where the currency was "admiration units".
There was some sort of extra-dimensional telepathic computer that credited or debited your account, based on how much you "admired" your transaction with another individual.