I have this Yahoo! Finance filter I run that looks for relatively stable companies that have fallen more than 25% in a trading session. Stocks that come up on that list I look at for industry strength, debt to capital ratio, and what roles they are hiring for. My preferred drop is 33%+. SPRY is one I picked up from that screen. My next step with these stocks to follow the price with JStock, dumping them if they keep falling and otherwise waiting for them to reach a point where I can sell off enough to cover my initial investment and still retain some shares. At that point, I set JStock for some extremes that may make me look again, and basically forget about it. If it does well, great. If it folds, I only lost maybe 30 minutes of time with research, trading, and writing it up here.
Back when I could track drops over several days I bought NVDA at ~$12. I wish they were all that good, but it was truly an exception and my main criteria for buying it was that I bought one of their video cards two years earlier.