Mark,
Faber suggests buying a basket of different futures markets and just rolling them over when expiration nears. Just make sure you go easy on the leverage so that normal fluctuations don't wipe you out.
The only true fund that I know of that buys actual commodities as an index is the one run by Jim Rogers. It's called the "Rogers International Commodity Index." For an individual investor the minimum investment is $10,000. Here's the link...
http://www.rogersrawmaterials.com/page1.html
Larry