Where can I find out more info on trading Commodities? (including historical data, ect)

I've read several books on trading Commodities. There has been allot of good information that I've learned. And as many people agree, knowledge is the key to being successful. Where can I find out more about trading Commodities; margin deposits, somewhere a paper trade simulator is available, and of course, hopefully, 5-10 years of historical data? (preferably low cost or free) I'm currently not ready to open an account. What I'm attempting to do is confirm what I think I know and validate the trading strategy that I'm considering using.

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