In the last trading session, U.S. stocks were mixed. Among the top ETFs, SPY gain 0.1%, DIA was up 0.5%, and QQQ moved 0.7% lower on the day.Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most-recent trading session. This could make these ETFs the ones to watch out for in the days ahead to see if this trend of extra-interest continues.AOA: Volume 7.27 Times AverageThis aggressive allocation ETF was in the spotlight as around 396,858 shares moved hands compared with an average 54,580 shares a day. We also saw great price movement as AOA added 0.45% in the last session. The big move was largely the result of a crash in the market last week, which supported the need for diversification. The fund has about 81.95% exposure to equities followed by 17.34% focus on fixed income. The fund was up 0.3% past month.SCHO: Volume 2.85 Times AverageThis government bond ETF was under the microscope as 3.14 million shares moved hands. This compares with average trading volume of roughly 1.10 million shares and came as SCHO added 0.2% in the last trading session. SCHO was flat in a month’s time.Want key ETF info delivered straight to your inbox?Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report SPDR SP 500 ETF (SPY): ETF Research Reports Invesco QQQ (QQQ): ETF Research Reports SPDR Dow Jones Industrial Average ETF (DIA): ETF Research Reports Schwab ShortTerm U.S. Treasury ETF (SCHO): ETF Research Reports iShares Core Aggressive Allocation ETF (AOA): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report