Then check out Richard Bloch's post in SEEKING ALPHA, "Betting With Jim Rogers: Beyond The Agricultural Stocks". Bloch describes in some detail Market Vectors' Hard Asset Producers ETF (HAP), which is based on the Rogers - Van Eck Hard Assets Producers Index :
This is an interesting index because it's designed to track the overall performance of a diverse set of more than 350 hard asset companies. So instead of simply weighting companies by market capitalization, the sectors are first defined into broad categories - allocated based on estimates of global demand and production.
The current sector weightings look like this: