A Yahoo! finance screen I have created to find stocks that have a big one-day drop but may still be viable. I still do some basic analysis and only buy from this list maybe 1 in 20 that it finds.
% Change in Price (Intraday):less than -20, Region: United States, Market Cap (Intraday): Mid Cap and Large Cap and Mega Cap and Small Cap, Volume:greater than 90000, Price (Intraday):greater than 2, Price / Earnings to Growth (P/E/G): < 1 and 1 to 2