The New York Times recently made a case for investing in stocks to gain exposure to commodities:

But there is an easy way to get a shot at commodity-like returns, without investing directly in commodities or their indexes. Investors can buy shares of the natural resource companies that produce commodities.

However, investors need to be careful: just because a stock is in a sector related to commodities doesn't mean that it will move with the prices of those commodities. Other factors, including decisions by management, any hedging the company may have in place, and other company-specific factors, may cause their returns to differ from those of the underlying commodities. While it's quite true that, as the New York Times points out, natural resources stocks have outperformed commodities in recent years, that is not a trend that will necessarily continue.

There may be good reasons to buy these stocks, but if you want to make a bet on commodities prices, the best way to do that is with exchange-traded funds (ETFs). Back in his days at the Motley Fool, BloggingStocks contributor (who is the source for news and analysis for private equity, by the way) Tom Taulli wrote a nice piece about how to invest in commodities through ETFs.

If you really want to learn about ETFs, I recommend picking up a copy of Investing with Exchange-Traded Funds Made Easy: Higher Returns with Lower Costs -- Do It Yourself Strategies without Paying Fund Managers by Marvin Appel.