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 5,400 starred companies, but they're just shy of superstardom. While all the attention might be focused on their five-star peers, we can sift through CAPS to find four-star firms approaching greatness. Here are a handful of four-star firms approaching greatness.

  • Alpha Natural Resources (NYSE:ANR)
  • Cytori Therapeutics (NASDAQ:CYTX)
  • ImmunoGen (NASDAQ:IMGN)
  • Stillwater Mining (NYSE:SWC)
  • US Bancorp (NYSE:USB)

Some of these names might surprise you. US Bancorp has generally been a model of conservative leadership during the financial crisis, which is probably partially why Warren Buffett increased his holdings. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold. However, the 125,000-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
As the largest producer of platinum group metals in North America, Stillwater Mining has felt the crushing blow delivered to automakers just as much as the car companies, their parts suppliers, and rental agencies have -- all of which have asked Washington for a handout to keep them afloat. Why not Stillwater too?

Platinum group metals, or PGMs, have their biggest market in the automotive industry, where platinum and palladium are used in the manufacture of catalytic converters for exhaust systems. After hitting a high of nearly $600 an ounce last March, the price of palladium has plummeted; it now trades for just more than a third of that, after having hit even deeper lows. As prices have fallen, Stillwater has had to resort to layoffs, and it's considering yet another round as it strives to stay right-sized and operate cost-effectively.

There's little doubt that palladium surpluses will keep prices depressed, and that Stillwater will have challenges at these lower levels. Yet there remains cause for hope. The spending bonanza being unleashed in Washington is stirring up concerns over inflation, and while most of the attention is being focused on gold and silver as a hard asset for safety, other precious metals, including palladium and platinum, may benefit as well. In addition to Stillwater, it may help other producers like North American Palladium (NYSE:PAL) to experience a "pop" as investors flee to safer havens.

Furthermore, while Stillwater Mining is the Western Hemisphere's biggest player, 80% of all palladium is produced in Russia and South Africa, giving them a large say in pricing. Considering the woes befalling its economy, it would be in Russia's interest to maintain tight control over the supply entering the market, thus providing a prop for prices.

Even the ailing auto industry holds out a beacon for Stillwater. The company has two long-term contracts with the auto industry; one, renegotiated in 2007, included minimum pricing levels and extended the length of the contract until 2012. Even if General Motors (NYSE:GM) or Chrysler were to go bankrupt, a restructuring could lead to a stronger auto industry.

Undoubtedly, investors will need patience for this to work out, but its size in the market and its depressed valuation make it attractive. CAPS All-Star member SuperPicks would seem to agree that with current economic conditions at work, Stillwater Mining can prove profitable, even if risks such as a strong dollar confront it:

Certain miners have been hit hard this past year. In current environment where the dollar is at relative highs, stimulus plans are being ushered out, and domestic production is being favored, the downsides may be neutralized. However an even stronger dollar will not be good for this company.

A great opportunity for you
With four-star investments seeminly on their way to five-star greatness, 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.

US Bancorp is a Motley Fool Income Investor pick. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.