Some companies are obviously great investments -- in hindsight. Sure, we should have bought Starbucks at its IPO and earned hundredfold returns over the years. 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 companies in the CAPS universe, but they're just shy of superstardom. While their five-star peers might draw all the attention, we can sift through CAPS to find four-star firms approaching greatness:

  • Bucyrus International (NASDAQ:BUCY)
  • SiRF Technology (NASDAQ:SIRF)
  • Mercadolibre (NASDAQ:MELI)
  • Mosaic (NYSE:MOS)
  • SanDisk (NASDAQ:SNDK)

Some of these names might surprise you. SanDisk memory cards, for example, are probably in your digital camera, mp3 player, and mobile phone. 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 84,000 CAPS investors chose these companies as less obvious sources for tomorrow's great buys, so let's see why they might merit your attention.

A coal-black heart
First the market smacked SiRF Technology over the head with a shovel after it reported an earnings miss earlier this month. Then investors seemed ready to use that shovel to bury the GPS chip maker, too. Shares dropped nearly 60% in one day, after SiRF reported profits of only $700,000, compared to $9.1 million the year before. Worse still for the company was its anticipated loss of $0.04 a share in the first quarter of 2008, compared to analyst projections of $0.24 per share in earnings.

Shares sank amid the market's concerns that prices for navigation device prices would pressure SiRF's margins. Demand remains high for personal navigation devices, but competition is getting stronger, too. The news had a ripple effect as well: Shares of GPS maker Garmin (NASDAQ:GRMN), a customer of SiRF, fell 8% as a result.

Looking a little further into the future, you still see Research In Motion (NASDAQ:RIMM), Sony, and even General Motors needing SiRF's technology for their own product offerings. Skeptics may be premature in planning for the specialized chip maker's demise.

That's certainly the feeling over on CAPS, where All-Star investors like lBluttol and PopsDaniecki, with 98.95 and 99.52 player ratings respectively, feel that the sell-off is overdone. With a balance sheet that's still relatively strong, SiRF could make an attractive takeover candidate at worst. According to lBluttol, "I say that SIRF is an absolute screaming buy here if only for one compelling reason: SIRF is now dirt cheap and a prime takeover candidate."

Another All-Star, ddberg, is worried about the earnings miss and the company's regular practice of share dilution. Still, the stock's recent hammering makes its current price an attractive entry point:

Unless I'm completely missing something, or there's more going on than is publicly known, this sell-off seems highly overdone. Share dilution: bad. Falling short of estimates: relatively bad. But a 50% 1-day drop for a company still looking at double-digit growth across the board that wasn't significantly over-valued beforehand? Seems extreme.

A great opportunity for you
You've heard the latest on SiRF Technology, but do you agree? Are these four-star stocks still investment-grade material? On Motley Fool CAPS, your input can ultimately influence how they're rated. Outperform or underperform, near-term or well in the future, your opinion counts.

Sign up today for Motley Fool CAPS; it's completely free. Let's us hear what you have to say about the great and almost-great companies that interest you.