After a 7% slump during October, and several big swings in November, it's safe to say that volatility is back in the stock market here in the final weeks of 2018. While the declines can make checking your portfolio a painful exercise, they have also generated some solid buying opportunities for patient investors.

With that in mind, below we'll consider eBay (EBAY -2.91%), Constellation Brands (STZ -0.44%), and Wayfair (W -3.57%), which look like bargains following their recent drops.

A man holding shopping bags.

Image source: Getty Images.

More than a marketplace

eBay shares are down over 20% so far in 2018 in a sell-off that looks like a classic overreaction by investors. Sure, the online marketplace isn't growing as quickly as management had hoped it would. Its sales volume slowed to a 5% rate last quarter from 7% in the prior quarter, even though executives had been targeting a slight acceleration. eBay's pool of buyers expanded at a 4% rate for the third straight quarter, too, making it less likely that the company can easily return to the healthier 5% pace it logged through most of 2017.

Yet eBay is still growing, both in its core marketplace segment and in its StubHub ticketing division. The broader business is set to dramatically improve on its market-thumping profitability over the next few quarters, too, as management turns its focus toward boosting efficiency and extracting value from promising initiatives like payment processing and third-party advertising. Even minor successes here are helping earnings march higher in 2018 despite the slower sales growth. And they're paving the way for increased shareholder returns in 2019 and beyond.

Beer, wine, and cannabis

Alcoholic beverage giant Constellation Brands might not look like a bargain at 21 times expected earnings, versus 20 and 13 for rivals Anheuser-Busch Inbev and Molson Coors, respectively. Yet the company, whose portfolio is tilted toward premium imported beers like Corona and Modelo, is growing much faster than these peers. Its beer volumes are up 10% so far this year, in fact, versus minor declines in most rival brands.

Two friends celebrating while holding beer bottles.

Image source: Getty Images.

Constellation Brands is boosting profits at a slower pace than usual right now, but only because the company is making big investments in marketing and advertising to support its biggest brands and the launch of its new Corona Premier franchise. That earnings hit is likely to fade away over time, leaving the company in position to extend its market-share lead even further.

Looking beyond just the next year or so, investors have good reasons to be optimistic about the recent brewery purchases and the $4 billion that the company is directing toward the consumer cannabis-product space. CEO Rob Sands and his team have a strong track record for making game-changing capital investments, after all.

A growing e-commerce specialist

Not long ago, Wayfair stock was above $150 per share and up almost 100% in 2018. Now the stock is barely beating the market and sitting below $90 per share.

What changed? Not much.

The e-commerce specialist revealed another quarter of market-thumping sales growth for the fiscal third quarter, as revenue jumped 43% to surpass management's optimistic forecast. And with repeat orders climbing as a percentage of total volume and the active customer base approaching 14 million, Wayfair is clearly making progress in consolidating its hold on the online home-furnishings niche.

The company hasn't booked a profit in any of the last five years, and its losses might even expand in 2018 compared with 2017. That track record makes this business a risky one to invest in, even following the stock's recent slump. However, investors who believe in management's bullish outlook should be happy to see the company doubling down on its growth strategies, since that's the clearest path toward substantial profits over the long term.