This Week's ETF Winners & Losers

Bundled securities tracking homebuilders, financials and REITs were the worst performers of a losing week for stocks as the health of the credit markets continued to deteriorate.

Among REIT-related ETFs, the iShares FTSE NAREIT Mortgage REITs (REM Quote) dropped 18.4% for the week to $32.11. The iShares FTSE NAREIT Retail (RTL Quote) ETF shed 4% to $39.04. The Ultra Real Estate ProShares (URE Quote) ETF slid 2.2% to $40.45.

In the financial sector, Bear Stearns (BSC Quote) was crushed following several negative headlines during the week. On Friday finance chief Sam Molinaro said during a conference call that the credit market was "about as bad as I've seen it in 22 years." The stock ended with an 11.7% loss on the week.

Other lenders and finance names fell hard, as well. Countrywide (CFC Quote), Lehman Brothers (LEH Quote) and Merrill Lynch (MER Quote) slid 6.5% or more.

The Rydex S&P Equal Weight Financials (RYF Quote) ETF dropped 3.3% to $45.17. The PowerShares Dynamic Financials (PFI Quote) ETF gave back 3.2% to $23.80. The First Trust Financials AlphaDex (FXO Quote) ETF ended down 2.7% to $17.71.

Homebuilders were also feeling the crunch. On Wednesday, Beazer Homes (BZH Quote) plunged as much as 40% and dragged down the rest of the homebuilding sector amid rumors the company was facing a liquidity problem. Beazer quickly moved to deny the speculation, but still ended with a 27% decline for the week.

The iShares Dow Jones U.S. Home Construction (ITB Quote) ETF tumbled 7% to $25.15. The SPDR S&P Homebuilders (XHB Quote) ETF finished the week lower by 5% to $25.44.

On the flipside, the PowerShares Lux Nanotech (PXN Quote) ETF was one of few winners during the week, thanks to gains in several of its holdings.

Among them, Arrowhead Research (ARWR Quote) surged 35%, and Accelrys (ACCL Quote) added 5.7% on the week. The PowerShares Lux Nanotech ETF climbed 3.9% to end the week at $17.10.