Believe it or not, there's a silver lining to the global downturn: falling oil prices.

Crude oil futures are down to about $90 a barrel and have plummeted even below that level at points this week. It's a pretty stunning drop compared with where we were just a few months ago. In July, the big story was $150-a-barrel oil and scary predictions of $200 crude and $6-a-gallon gasoline.

While this might be cold comfort as the Dow sheds hundreds of points daily, for investors with a strong stomach and contrarian bent, falling oil prices present some intriguing opportunities.

"You have to look at this collapsing price of oil as one of the biggest tax cuts ever to consumers and businesses alike," Bob Froehlich, chief investment strategist and vice chairman of DWS Investments, said in a recent market commentary. "When oil is down, mergers are typically up; and when interest rates are down it's only a matter of time until the market is up as well."

Even with the Federal Reserve and other central banks cutting interest rates, the global economy is still slowing and consuming less oil. If you think lower crude prices will stick for a while, here's how to best take advantage of the decline.

Materials

Investors have whipped basic-materials producers pretty hard because of recession fears, but consider how much these guys will benefit from lower oil prices. For the chemical industry alone, "the biggest cost input is petroleum-based products," Froehlich says. One company to consider: Dow Chemical (DOW), which is trading in the high $20s. Morningstar recently put its fair value at $50 and said it's worth a look at $32.50, although uncertainty is "high."

Other Commodities

The world can drive and build less, but it can't stop eating. This means wheat, corn, soybean, cattle and other livestock are still in the mix. "The fundamental story that got lost is that 'feed the world' has always been bigger than 'fueling the world.' We've got about more than a billion people around the world coming out of poverty over the next five to six years, and when that happens they change the quality and quantity of food they eat, not their mode of transportation," Froehlich says. Also, don't forget gold. "Gold has always been a really good hedge for the strife," says Carlton Neel, portfolio manager of the Virtus Alternatives Diversifier (PDPAX) fund, which invests in "alternative" asset classes like real estate and natural resources. Consider ETFs for broad exposure.

Consumer Discretionary

Oddly, consumer-discretionary stocks beat the S&P 500 by 500 basis points through Monday, which may be a sign some investors are already trying to play falling oil. However, housing prices and unemployment make this area more dicey. If you do wade in here, Froehlich suggests a "barbell" strategy, meaning you go either very high-end or very low-end. High-end retailers like Tiffany (TIF) might suffer less, but cost-savers like Wal-Mart Stores (WMT), Target (TGT) and McDonald's (MCD) "will be the beneficiaries of the oil tax cut," he says.