U.S. stock markets finally regained their sense of optimism today, as broad markets ended up higher across the board. The Dow Jones Industrial Average (INDEX: ^DJI) added 135 points, notching a cool 1.1% during the trading session. Putting the Dow to shame, the S&P 500 and tech-weighted Nasdaq rallied 1.6% and 2.5%, respectively. Perhaps in the most telling sign, the market's so-called "fear gauge," or the VIX (INDEX: ^VIX), plummeted 12.3% today, signaling that investors shed many of their concerns that weighed so heavily throughout last week.

Around the markets
Some of today's most intriguing storylines came out of the tech sector. Apple (Nasdaq: AAPL) skyrocketed today, helping to dispel investors' fears that the tech giant's momentum had all but run out after an extremely strong last six months that saw its jump nearly 50%. On the flipside, investors in social-networking darling Facebook are probably licking their wounds. Coming off an IPO performance last Friday that would be generously described as lackluster, Facebook fell off a cliff today, plummeting around 11%.

And while we're on the topic of massive swings, two nat-gas plays also made waves today. Both Westport Innovations (Nasdaq: WPRT) and Clean Energy Fuels (Nasdaq: CLNE) spiked substantially higher during today's trading session. News came from European automaker Volvo that it will begin using Westport's 13-liter engines in some of its heavy-duty trucks. Clean Energy's pop came without a clear catalyst. However, seeing both stocks surging so grandly today does highlight the central theme many investors have for buying into natural gas investments: The stuff's downright cheap. And with oil prices looking less than-cheap, investors are hoping producers could shift their purchasing in favor of nat gas.

What it all means
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