There are a number of broad-based and targeted commodities ETFs. The largest broad ones are:

* iShares S&P GSCI Commodity Indexed Trust (GSG) tracks a broad index of 24 commodities weighted according to the proportion of the commodity flowing through the economy. Almost half of the index reflects crude oil, and the balance is split between other energy products such as natural gas as well as agricultural commodities, industrial and precious metals, and livestock.
* An even more diversified commodity play is the iPath Dow Jones-AIG Commodity Index Fund ETN (DJP), which tracks an index that comprises 30% energy, 30% agricultural, 20% industrial metals, 10% livestock and 10% precious metals.
* PowerShares DB Commodity Index Tracking Fund (DBC) tracks the futures for a simplified index of just six commodities: corn, crude oil, gold, heating oil, aluminum and wheat.

Which one is “best” depends on the kind of exposure you’d like to certain areas, as well as your overall portfolio and goals.

For more information about commodities investing, our special report has a lot of information:
http://www.etftrends.com/2008/05/commodity-speci.html

There are some short agriculture and commodity ETNs available, which launched earlier this year:

DB Agriculture Double Short ETN (AGA)
DB Agriculture Short ETN (ADZ)
DB Commodity Double Short ETN (DEE)
DB Commodity Short ETN (DDP)
PowerShares DB Agriculture Double Long ETN (DAG)
PowerShares DB Agriculture Long ETN (AGF)
PowerShares DB Commodity Double Long ETN (DYY)
PowerShares DB Commodity Long ETN (DPU)

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