Prices of everything from gold to oil to corn are falling fast. Here's how you can benefit.

FORTUNE – Commodities are falling fast on worries that China's economy is slowing and that the economic recovery in parts of Europe and elsewhere has stalled. Copper has sunk to a three-year low, falling below $7,000 a ton in April. For the first time since last July, Brent crude oil fell below $100 a barrel as demand for fuel weakened across slower-growing economies. And after record highs last summer as America's heartland suffered one of the worst droughts in decades, corn prices have plunged as farmers set about to plant one of their biggest harvests in years.

Traders betting that commodities would rise might be hurting today, but the decline in prices could bring relief to America's consumers. And while the fall in gold prices signals many economies could be in trouble, it may very well be something to celebrate.

Here are three reasons the average consumer should cheer falling commodities:

Bigger retail sales

Lower gasoline prices may be signaling slower growth throughout the world's major economies, but they have also left U.S. consumers with some extra spending money.

What they aren't spending to refuel their cars, they're spending on everything from electronics to clothes. In April, retail sales unexpectedly edged up 0.1% after a 0.5% decline in March. 

Declining gasoline prices, which fell 14 cents in April, have helped offset some of the drag from higher taxes that kicked in January. Receipts at clothing stores recorded their biggest increase since February last year. Consumers also spent more at restaurants and bars. 

Nationwide, gasoline prices are expected to fall through summer -- the result of a spike in crude oil production. A gallon of regular gas will cost about $3.50 this summer, down more than 10 cents from last year, according to the U.S. Energy Department.

Happier stockholders

Investors typically see gold as a hedge against rapidly rising prices. But with global inflation falling, gold prices have tumbled -- officially entering a bear market last month.

U.S. stockholders have gained as prices for the yellow metal decline. To be sure, only about half of Americans own any stock, but those who have money invested are benefetting in big ways. The S&P 500 (SPX) is up 16% so far this year and has continued to soar to new highs. With U.S. inflation lower than the Fed's target of 2%, stocks may rise further as it's less likely the central bank will end its large-scale bond purchasing plans any time soon.

Lower grocery bills

The decline in corn, soybean, and wheat prices may have left some traders scrambling, but it should bring good news to shoppers in U.S. grocery stores. 

Farmers this year are expected to harvest record crops, after recovering from the worst drought to ravage the industry in decades. With bigger supplies, corn prices are forecast to average $4.80 per bushel, down a third from the previous year's average, according to the U.S. Department of Agriculture. Corn prices are closely tied to supermarket prices, since it's a key ingredient in many foods and used as feed for livestock. Soybeans are expected to average $10.50 a bushel, down 27%; wheat is forecast to decline by 11% to $7 a bushel. 

To be sure, we won't likely see a drop in grocery prices this year, but the increases will be smaller compared to levels reached in 2008 and 2011. Food prices will increase between 3% to 4% in 2013, as higher feed prices from the drought continue working through animal-based food products. That's slower than the 6% rise in 2011 and the 8%-9% jump in 2011. Hopefully by 2014, we'll reap the real benefits of this year's drop in corn and wheat prices.