This is part 2 of several installments of our look back at the topics and trends that have been important and interesting to investors in the first half of 2006. Check out our first one on the economy, and then stay tuned all this week for additional articles in this series.

One of the most prevalent trends so far this year has been a move toward "green" lifestyle choices. "Green" isn't limited to describing things such as hybrid cars and organic food, though. Investors have picked up on the idea that "green" can translate into more green for their portfolios, too. So whether you're a consumer shopping for the latest organic produce or an investor shopping for a retailer to add to your portfolio -- or, heck, both! -- check out our collection of articles below to discover what we've said about three green trends (organic foods, alternative energy, and hybrid vehicles) so far this year.

Trend: Organic foods

The Greening of Wal-Mart?

By Brian Gorman

Wal-Mart (NYSE:WMT): Always low prices! Always ... organic?

The world's biggest retailer is reportedly planning to double the number of organic grocery items it offers. The new products may not steal Whole Foods' (NASDAQ:WFMI) loyal customers in droves, but even if it doesn't directly translate into huge sales, offering more environment- and health-friendly groceries should help Wal-Mart continue to grow. . (For more, click here.)

Dean's Organic Dilemma

By Adrian Rush (TMF Squiggly)

What's in a name? Specifically, when the subject is the food industry and the name is "organic," what do you think of? Do you think of healthy, green crops basking in the sun, and cows happily grazing in the pasture? Or do you think of mass-produced foods and cows lined up in feedlots?

That's the dilemma facing Dean Foods' (NYSE:DF) Horizon brand, which is being accused of riding the organic bandwagon but acting like a factory farm. The Organic Consumers Association, which has organized a boycott of Horizon, says the company is threatening to put small family farms out of business by operating organic dairies so massive in scale that traditional mom-and-pop farms can't hope to compete. . (For more, click here.)

Whole Foods Thinks Small

By Alyce Lomax (TMF Lomax)

With Wal-Mart's behemoth powers breathing down the neck of the organic movement, Whole Foods Market's recent pledge to support small farms is no surprise, even as it comes on the heels of heated criticism from a foodie author. After all, many of the people who are fans of the organic movement have pointed out the fact that as organic living grows more popular, industrialization threatens to co-opt the original intent. . (For more, click here.)

Tom's Deal With the Devil

By Adrian Rush (TMF Squiggly)

Is socially responsible investing possible?

The perennial question comes to the fore once again with news that Colgate-Palmolive (NYSE:CL) has purchased a controlling stake in little Tom's of Maine, a brand known as much for its personal-care products as for its social conscience. . (For more, click here.)

Trend: Alternative energy

Searching for an Energy Revolution

By Robert Aronen

The run-up in oil and gasoline prices over the past few years has caused a renewed interest in alternative energy, both in the United States and around the world. For both economic and environmental reasons, many companies are looking for new ways to meet our energy demands. Will one of them create a world-changing solution to our energy woes? . (For more, click here.)

An 11-Bagger With a Suntan

By Tim Beyers (TMF Mile High)

California's public utilities commission approved a $2.9 billion initiative to harness 3,000 megawatts of solar power over the next 11 years. Getting there, regulators figure, will require one million installations of rooftop solar panels. They'll be everywhere, too -- homes, businesses, farms, schools, and public buildings, according to Reuters. . (For more, click here.)

Switchgrass in the Spotlight

By Robert Aronen

As part of his macro-plan for the nation, President Bush introduced us during his State of the Union address to a forgotten native of the American prairie -- switchgrass. Trying to stick with my New Year's resolution to pay attention, I decided to find out whether switchgrass could form a significant part of our future fuel supply. . (For more, click here.)

Is Ethanol Worth the Hype?

By Ryan Fuhrmann, CFA

Clearly, there are merits to producing ethanol and using it as an alternative to oil-based gasoline. It would most definitely benefit domestic farmers with a huge new market to sell corn into. It would also reduce American dependence on oil from the geopolitically charged Middle East.

On the flipside, it's unclear whether ethanol is, or will be, more affordable than gasoline. . (For more, click here.)

Trend: Hybrid vehicles

Hybrid Help for GM?

By Brian Gorman

As gas prices reach new altitudes, conventional wisdom has it that the heyday of big vehicles is over. Recent developments at the automakers seem to back up this notion -- but a new technology may make the eulogy for gigantic cars a bit premature. . (For more, click here.)

Ford's Green Machine

By Brian Gorman

Ford (NYSE:F) is working hard on an image makeover, seeking to establish itself as the leader in environmentally-friendly vehicles. Financiers might condemn Ford's latest move, but it could contribute to the company's long-term vision. . (For more, click here.)

Detroit's Stealth Subsidy

By Rich Smith (TMF Ditty)

Ever since 1999, buyers of hybrid vehicles such as the Toyota (NYSE:TM) Prius, the Honda (NYSE:HMC) Civic hybrid, and the Ford Escape hybrid have been able to use a $2,000 income tax deduction as partial compensation for the added cost of a hybrid package (on average, $2,500 to $5,000 more than non-hybrid equivalents). In tax year 2006, that $2,000 deduction gets upgraded to a tax credit of $250 to $3,400. . (For more, click here.)

Whole Foods is a Motley Fool Stock Advisor recommendation, while Wal-Mart and Colgate-Palmolive have been given the nod from Motley Fool Inside Value . You can try any of our newsletters for free for 30 days, and if you're not happy, there's never an obligation to buy.

The Motley Fool's disclosure policy is as green as they come.