Do you know what still gets me about the stock market crash?

Somebody out there made a bundle off it.

I know, it's hard to believe. Most folks' retirement account balances are still way down, despite the strong rally we've had since early March. Every single stock mutual fund (all 11,579 of them) was down in 2008, and highfliers from Alcoa (NYSE: AA) to American Oriental Bioengineering (NYSE: AOB) -- and that's just the beginning of the alphabet -- are still way off their highs.

But somewhere out there are investors who made money in 2008 and early 2009. Lots of money, in some cases.

Many are professionals, of course -- hedge fund managers and others with access to sophisticated tools and strategies -- but others are just ordinary individual investors like you and me. Like you and me ... except that they've learned to use tools and strategies we haven't.

Like going short.

The long and short of it
Most mutual funds aren't allowed to short stocks -- to borrow and sell them, in other words, betting that they'll be able to buy the stock back at a lower price and make money on the difference. Many individual investors avoid the practice as well. The risks are high, the upside is limited, and shorting can't be done at all without a margin account, which excludes most retirement accounts.

But sometimes shorting a stock -- or a sector, or an index -- is a prudent investment. Markets go down as well as up, as we've seen recently. Sectors fall out of favor. Companies sometimes appear headed for disaster long before the wider market catches on, as was the case with Lehman Brothers for a while. Bubbles appear, become evident to some, and then pop.

Shorting banks, oil, or other commodities in mid-2008 would have been an excellent move, and the weaknesses in all three of those areas were visible to some folks at the time. But how many profited? A lot fewer, because shorting is dicey, and, as I mentioned previously, it's a strategy unavailable to most who do their investing via IRA accounts.

But that has been changing. New tools allow investors to take short positions without the need for a margin account. These offer great opportunities for the informed -- along with some new risks.

Enter the short ETF
Most investors are familiar with exchange-traded funds. ETFs track a wide variety of indexes and are traded throughout the day, like stocks. In recent years, companies like ProShares have created families of short ETFs -- investments that go up when the indices they track go down. (And -- this is important -- vice versa.)

The selection has grown rapidly. ProShares alone offers an extensive selection covering all the major U.S. and international indices, sectors from financials to industrials to health care, commodities including gold and crude oil, major currencies, and more. Continued...