Exchange-traded funds tracking the financial sector were among the biggest winners this week, propelled by the Federal Reserve's decision to cut its overnight lending rate by another quarter-point to 2%.

The Ultra Financials ProShares ( UYG) had a particularly good week, surging 5.2% since Monday.

At the same time, the Financial Select Sector SPDR ( XLF), the Vanguard Financials ETF ( VFH), the iShares Dow Jones U.S. Financial Sector ( IYF) fund and the iShares S&P Global Financials ( IXG) ETF each added 2.3% or more.

The central bank provided further cushion to financials Friday when it ratcheted up its term auction facility by 50% to $150 billion, meaning banks will have that much more money available for borrowing.

Since Monday, two of the Dow's financial components -- Bank of America ( BAC) and JPMorgan Chase ( JPM) -- added 3.9% and 1.8%, respectively, though Citigroup ( C) ticked 0.8% lower, weighed down by this week's news that it would offer $4.5 billion in stock.

Suffering the flip-side of the Fed's decision were commodities-related ETFs. Among the worst-performing energy ETFs were Oil Services HOLDRs ( OIH), PowerShares Dynamic Oil & Gas Services ( PXJ), United States Oil ( USO) and iShares Dow Jones U.S. Energy ( IYE). All have sunk at least 2.1% apiece over the past five sessions.

Those declines came despite climbs at Chevron ( CVX) and BP ( BP), which both reported higher profits this week on the back of the oil boom, and for the week were up 2.8% and 4.4%, respectively.

Exxon Mobil ( XOM) was a notable exception, sliding 3.1% since Monday after failing to hit analyst estimates for the first quarter, despite a surging bottom line.

As for gold, the Market Vectors Gold Miners ETF ( GDX) slid 4.7% for the week, while the iShares COMEX Gold Trust ( IAU) and the streetTRACKS Gold Shares ( GLD) fund each dropped 3.1%.

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