If you simply looked at the -20% drop in shares of Leapfrog (NYSE: LF) this morning, you’d think that the educational toy maker had lost its way. Yes, the company’s quarterly sales and profit results trailed forecasts, but they still represented a sharp improvement from year-ago results. Considering many investors had written this company off as a goner just 18 months ago when sales were in freefall and operating losses were seemingly open-ended, +42% year-over-year sales growth in the first quarter has to be considered a victory.

Of course, some of the shareholder base exiting the stock this morning jumped in when Leapfrog posted scorching results last quarter, which is the company’s seasonally most important period. But make no mistake, management has helped fuel a remarkable turnaround by maintaining investments in R&D that are now paying off. Rivals such as Mattel (NYSE: MAT) and Hasbro (NYSE: HAS) have had a number of years now to try and dethrone Leapfrog and its various “edutaining” platforms (the nexus of entertainment and education). Now that Leapfrog looks healthier – and not likely to be quashed by competitors—investors have a chance to buy into a name that appears poised for respectable 15% to 20% sales growth, and more robust profit growth.

Leapfrog remains on track to boost per-share profits back toward the $0.50 mark by next year, and once management outlines the roadmap for future R&D plans (as they often do each summer), then shares may rise toward a 20 times multiple on projected 2011 profits, or $10 a share. That’s some 80% ahead of today’s lower trading price. (Notably, analysts at Needham & Co. just raised their 2011 profit forecasts above that $0.50 consensus, to $0.60).

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Investors in Alvarion (Nasdaq: ALVR) are abandoning ship. The Tel Aviv-based company has held so much promise, but another weak quarter has led some to question whether the company can ever build a head of steam. Alvarion makes WiMax equipment, which is used to deliver high-speed internet access – just like with WiFi, but over entire regions. Around the globe, WiMax has garnered a great deal of buzz, with backing from firms like Intel (Nasdaq: INTC) and Google (Nasdaq: GOOG). Here at home, Clearwire (Nasdaq: CLWR) is betting its entire business plan on WiMax.

But WiMax has company. A technology called LTE (Long-Term Evolution) is gaining increasing favor with incumbent wireless service providers, though WiMax has a 12-18 month head start on deployments. But that head start isn’t boosting Alvarion, which actually saw sales decline sequentially in the most recent quarter. Shares are off roughly -15% this morning, continuing a slide that began three weeks ago.

Value investors may be tempted to bottom-fish, as the company’s $103 million cash stash is almost half of the company’s value. But there’s no hurry. Shares are likely to mark time for at least another quarter as management cuts staff and re-positions the company’s marketing efforts. That said, Alvarion has long been the subject of buyout rumors, so anything can happen.

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Many firms have the bad luck to report fairly impressive quarterly results on a day when the markets are down sharply. These stocks are feeling gravity’s pull. Yet these weak trading days are a great source of ideas for new investments that have been oversold in a market downdraft. Companies that are reporting decent results, yet are seeing their shares fall by more than 5% include Domino’s Pizza (NYSE: DPZ), Westlake Chemical (NYSE: WLK), and DineEquity (NYSE: DIN).