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 all the attention might be focused on their five-star colleagues, we can sift through CAPS to find four-star firms approaching greatness:

  • Sierra Wireless (Nasdaq: SWIR)
  • TBS International (Nasdaq: TBSI)
  • Quintana Maritime (Nasdaq: QMAR)
  • CapitalSource (NYSE: CSE)
  • Rochester Medical (Nasdaq: ROCM)

Some of these names might surprise you. Rochester Medical, for example, may seem too small to be great. Yet even small, undiscovered companies that we might not have ever heard of can offer great opportunities. Perhaps we just haven't realized their potential. However, the 80,000 CAPS investors chose these companies as less obvious sources for tomorrow's great buys, so let's see why they might merit your attention.

Walking the high wire
No longer is it a wired world we live in. The future is wireless, and being able to connect anything anywhere will prove who comes out on top. Doing so at blazing speeds will also be a requirement. Email, file and video sharing, and even simple web browsing is no longer reserved for computers and laptops, and doing all that from your phone is becoming almost as essential. With the latest generation of communication technology, it is readily possible -- but only if you've got the wherewithal to access it.

That's where Sierra Wireless comes in. It makes the modems that allow you to connect anytime, anywhere. Sienna sells its wares to Verizon and Sprint Nextel (for use on networks), as well as Hewlett-Packard (NYSE: HPQ) and Lenovo (for use in computers). Sierra has been enjoying some margin expansion, with net margins increasing by more than 40% over the past year on a rolling twelve-month basis. Prime competitor Novatel Wireless has also seen increased margins, and that's attracting attention from other rivals like Qualcomm (Nasdaq: QCOM), which recently unveiled its own Gobi mobile Internet card.

As more competitors enter, you can probably expect Sierra's margins to begin to narrow, but there's still plenty of opportunity for several players to grow. It's the industry's growth which has attracted CAPS investors like tsr401k, who sees it as a better play than Novatel. Interestingly, the two companies' shares seemingly move in lockstep with each other. While he might have been a bit exuberant about share price growth in this market, the fundamentals cited remain constant. Here's part of his pitch from last October.

[Sierra] is in a field that is growing at 50% [compound annual growth rate], they have raised and beat there raised guidance for the past 3 quarters ... 150 mil cash, no debt, beating est. new products. contracts with all the big carriers here and many international carriers ... competitor [Novatel] ... have 2mill more shares outstanding and 50 mil less cash than [Sierra] ... they [already] raised guidance for this qtr. i see this at 25 next week after earnings and 30 by the end of the year.

Other investors endorse Sierra because they believe wireless will take off this year, but also because it looks like a buyout candidate. From Hushuobadao:

Sierra [develops] and markets a range of products that include wireless modems for mobile computers, embedded modules for OEM's, and rugged vehicle-mounted modems. It also provides wireless wide area modem solutions for mobile computing. I believe 2008 will be the year of telecommunications acquisitions and mergers.

A great opportunity for you
You've heard from some CAPS players about Sierra Wireless, but do you agree? Are these four-star stocks still investment-grade material? On Motley Fool CAPS, you can give your input, which 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 is completely free. Let's us hear what you have to say about the great and almost great companies that interest you.

Sprint is a Motley Fool Inside Value recommendation. CapitalSource is a Motley Fool Income Investor pick. You can get a 30-day free trial to any of the Fool's investment services.

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.