ProShares UltraShort Euro ETF (EUO) +8.8%

The "flash crash" that sent the Dow tumbling nearly 1,000 points late Thursday took the wind out of nearly every traditional ETF product available. Although the market recovered a large portion of that initial drop minutes after the initial free fall, it still was a terrible week for stocks.

The main culprit for the drop in the past week was the Greek debt crisis, which put pressure on the euro, sending the double-short euro ETF higher. The winners list was littered with leveraged funds this week. For instance, ProShares UltraShort Emerging Markets ETF ( EEV) was one of the biggest gainers for the week, jumping 19.6%.

iPath S&P 500 VIX Short Term Futures ETN (VXX) +37.8%

The VIX has struggled to gain a footing over the past few months as bulls continued to power the market on an almost uninterrupted upward trajectory. However, this week, fear took over in a big way, helping VXX recover to levels last seen in the final days of February.

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iShares MSCI Spain Index Fund (EWP) -15.3%

Europe-based ETFs continue to feel the heat as Greece issues remain unsolved. Equity markets there sold off heavily, and foreign investors suffered doubly as the euro tumbled.

This week, EWP took the biggest hit among these funds. It had been trading sideways since hitting lows in early February, but the past two weeks of drops have erased the last year's worth of gains.

I don't expect the issues in Europe to be solved overnight. Investors should steer clear of EWP and other Europe focused ETFs for the time being.

Market Vectors Russia ETF (RSX) -15.5%

The Russian markets were not immune from the troubles facing Europe this week. The energy-heavy ETF designed to track the nation managed to break below its 200-day moving average as oil prices sank below $80 a barrel.

Though the past week has been tough for RSX, the longer outlook for the nation's markets still looks promising.

Claymore/MAC Global Solar Energy Index ETF (TAN) -15.8%

The solar energy industry took a beating this week with TAN breaking below a level which, since May 2009, has been a closely watched area of support.

As nations around the world work out their sovereign debt issues, subsidies for alternative energy will remain threatened. Stay clear of TAN until there is sign that the fund's free fall is finished.

Market Vectors Coal ETF (KOL) -11.7%

Coal companies have struggled to find a footing in May. This week, KOL broke below its 200-day moving average to retest February lows.

KOL has had a nice run as the global economy continued on the road to recovery. Although I remain confident that recovery is still intact, the outlook for KOL is cloudy. It recently dropped the fund from my ETF Action portfolio.

At the time of publication, Dion Money Management owned RSX.

-- Written by Don Dion in Williamstown, Mass.

Don Dion is president and founder of Dion Money Management, a fee-based investment advisory firm to affluent individuals, families and nonprofit organizations, where he is responsible for setting investment policy, creating custom portfolios and overseeing the performance of client accounts. Founded in 1996 and based in Williamstown, Mass., Dion Money Management manages assets for clients in 49 states and 11 countries. Dion is a licensed attorney in Massachusetts and Maine and has more than 25 years' experience working in the financial markets, having founded and run two publicly traded companies before establishing Dion Money Management.

Dion also is publisher of the Fidelity Independent Adviser family of newsletters, which provides to a broad range of investors his commentary on the financial markets, with a specific emphasis on mutual funds and exchange-traded funds. With more than 100,000 subscribers in the U.S. and 29 other countries, Fidelity Independent Adviser publishes six monthly newsletters and three weekly newsletters. Its flagship publication, Fidelity Independent Adviser, has been published monthly for 11 years and reaches 40,000 subscribers.