Some companies are obviously great investments -- in hindsight. Yet for every stock out there screaming "buy me," others simply give us a nudge and a nod. How can we tell tomorrow's obviously great investments from the thousands of pretenders?

The stars' walk of fame
On Motley Fool CAPS, these opportunities can be found among our four-star stocks. In CAPS' proprietary ratings system, they rank higher than most of the other 5,300 starred companies, but they're just shy of superstardom. While their five-star peers might hog all the attention, we can sift through CAPS to find four-star firms approaching greatness. Here are a handful of four-star firms approaching greatness.

  • A-Power Energy Generation Systems (NASDAQ:APWR)
  • Crosstex Energy (NASDAQ:XTXI)
  • DRDGOLD (NASDAQ:DROOY)
  • Echelon (NASDAQ:ELON)
  • Internap Network Services (NASDAQ:INAP)

Some of these names might surprise you. Smart grid leader Echelon, for example, is in the forefront of providing energy-aware devices that will help businesses and individuals save money and make smarter energy decisions. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold. Nonetheless, the135,000-plus CAPS members chose these companies as less obvious sources for tomorrow's great buys, so let's see why they might merit your attention.

In the sight of greatness?
Since the Pickens Plan was unveiled a year ago, wind power seems to have had the, um, wind taken out of its sails. Lower electricity demand, lower prices for traditional energy alternatives (oil and natural gas), still-tight credit markets that make financing difficult, and a lack of equity investors after the demise of Lehman Brothers and Wachovia mean that this promising technology might be like a schooner stranded on becalmed seas.

Shares of A-Power Energy Generation Systems, a Chinese wind turbine manufacturer, caught a breeze in early March, quintupling in value. However, a disappointing earnings report in June, followed by a $40 million debt sale plan, knocked them lower once again. The stock remains more than 60% below its 52-week high, much worse than the overall CAPS Wind Power sector, which is down just 28% on average over that same time frame.

Yet that earnings report also contains the first puffs of air that ought to fill out A-Power's sails again, generating a new pop in its price. The company booked its first sales contract; it'll be shipping two 2.7-megawatt turbines to the Daxinglong Mountain wind power generation plant in Jinzhou City. Moreover, the city of Shenyang announced that it's investing $44 million into a distributed power generation joint venture in which A-Power holds a 60% majority stake.

That's caused A-Power to raise full-year 2009 guidance for both earnings and revenue by 10%. What was once a speculative Chinese venture seems to be turning into a viable business with compelling growth prospects.

Blowing your doors off
China has doubled its wind capacity every year since 2006, and it's planning to spend $146 billion on seven wind farms with a combined capacity of more than 120 gigawatts. Citigroup estimates that the country's wind power capacity could readily achieve 130 gigawatts by 2020.

The United States currently is the world's biggest blowhard, with wind power capacity of 25,369 megawatts as of the end of 2008. The hardscrabble plains of Texas lead the nation with an installed base of 2,671 megawatts. Wind power comprises 42% of all the new electricity-generating projects being undertaken nationwide, even though it only represents 2% of the country's total power generation.

CAPS member uswdeng feels that analysts have overlooked the growth potential of A-Power, which he believes is a dominant force in China's energy future.

APWR is more intrinsic to economic development through the electric grid build-out and alternative energy development in China than many analysts seem to give credit. APWR's dominance in their business will prove rewarding to those of us with the patience to hold.

However, CAPS analysts have certainly not overlooked A-Power. It's one of the top 10 most-rated stocks in the Wind Power sector, behind other industry players such as Zoltek (NASDAQ:ZOLT) and Motley Fool Hidden Gems recommendation Otter Tail, but ahead of Xcel Energy (NYSE:XEL) and Broadwind.

A great opportunity for you
Investor sentiment suggests that these four-star investments still seem to be on their way to five-star greatness. Still, it pays to start your own research on these stocks on Motley Fool CAPS. Read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made, all from a stock's CAPS page.

Sign up today for the completely free service, and let us hear what you have to say about the great and almost-great companies that interest you.

Otter Tail is a Motley Fool Hidden Gems recommendation. Try any of our Foolish newsletter services today, free for 30 days.

Fool contributor Rich Duprey owns shares of DRDGOLD but does not have a financial position in any of the other stocks mentioned in this article. You can see his holdings here. The Motley Fool has a gold-plated disclosure policy.