Forgive me chiming in with an admittedly esoteric viewpoint... but...
What if "money" was a system of measurement, without intrinsic value...? What I'm envisioning is a barter economy, regulated somewhat like communistic states do -- but using a standardized system of worth-measurement.
So, say I had bricks of cheese, and you had boxes of eggs. Given that my cheese is say 0.5kg/brick, and you have 12 eggs to a box, we'd look up how much the gov't says our relative goods are worth, and exchange proportionately. So, say, one kg of cheese is worth ten credits that day, and three eggs is worth one credit, so I'd get fifteen eggs per brick of cheese, or five boxes of eggs for every four bricks of cheese if I've got my math right (sorry, I'm severely math-challenged -- to the level of having some sort of otherwise-unnamed "math fluency disorder" that I was labeled with in grade school... the gist is that I understand the *concepts* on actually something of a slightly advanced level, but I can't manage the actual *exercises*, real-world or textbook, without a half-decent calculator).
Alternatively, in a less-regulated society, we'd haggle for a while and figure out for ourselves what eggs and cheese should be worth -- although that somewhat sidesteps the need for standardized units altogether. Of course, that one guy who only has stuff that absolutely nobody wants, kinda gets into a bit of trouble in a barter economy... the conceptual system is not without its flaws. But, hey, that's true of everything out there, so... I dunno. /shrug