I don't currently subsrcibe to any charting services, but is there any easy way to overlay charts of DOW, or S and P with a commodity index, or a specific grain?  Any free sites that would allow one to do that?

I want to know if there is any truth to the concept that equities and commodities are counter cyclical.  It seems to me that in this recent era (~10 years) of bubble blowing that the rising tide seems to float all boats so to speak, although perhaps not equitably or at the exact same time.  Thinking back to the 2008 run up/down for example.