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, you'll find many such opportunities for future success 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 command the lion's share of investors' attention, we can sift through CAPS to find four-star companies approaching greatness. Here are just a handful:

  • Aircastle (NYSE:AYR)
  • Elan (NYSE:ELN)
  • IntercontinentalExchange (NYSE:ICE)
  • Paragon Shipping (NASDAQ:PRGN)
  • Petrohawk Energy (NYSE:HK)

Some of these names might surprise you. Elan, for example, has been in the forefront of the biotech industry for years. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold. The 130,000-plus CAPS members chose these companies as less obvious sources for tomorrow's great buys; let's see why they might merit your attention.

In the sight of greatness
The $450 million in bonuses that American International Group (NYSE:AIG) is readying for payout has understandably generated outrage and consternation. The corporate symbol of some of the past year's worst financial excesses is set to reward the very people who undid the once-great insurance giant -- with taxpayer money, no less.

AIG's exposure to credit default swaps ultimately sunk it. Without enough collateral to fulfill the provisions in those contracts, AIG suffered massive losses on its mortgage investments. There is plenty of blame to go around in this matter: disgraced former New York Governor Eliot Spitzer, who forced AIG's board to fire CEO Hank Greenberg; management that jumped into housing in a way that Greenberg never did; meddlesome politicians and regulators; and a system that most people barely understood to begin with.

But the fog shrouding the credit default swap market may finally be lifting. IntercontinentalExchange has begun operating a new central clearinghouse called ICE Trust Europe, which will act as central counterparty for credit default swaps, contracts that insure against the default of debt issuers. ICE is being joined by CME Group (NYSE:CME), which will launch its own effort.

Aside from its role in the AIG fiasco, the credit default swap market has generally been blamed for helping to exacerbate the credit crisis here in the U.S. ICE and CME suggest that by creating these clearinghouses, they will stand as a neutral, transparent counterparty between buyers and sellers of credit default swaps, thus ensuring that the trades will always be completed. By taking on the risk that either party to the transaction will default, the exchanges hope to reap large rewards in the $30 trillion market for such swaps. One industry consultant has estimated that credit-default-swap clearinghouses will generate about $100 million in revenue in 2009, and $138 million by 2011.

Like many other investors, CAPS member AuburnFool thinks this business could have a bright future: "I like the potential business growth for ICE in the CDS market. I think the management will work aggressively to grow the business."

A great opportunity for you
With these four-star investments seemingly on their way to five-star greatness, it pays to start your own research 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.

Elan is a Motley Fool Rule Breakers selection. Try any of our Foolish newsletter services 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. The Motley Fool has a disclosure policy.