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 companies approaching greatness. Here are a handful.

  • 3M (NYSE: MMM)
  • Alcoa (NYSE: AA)
  • British American Tobacco (AMEX: BTI)
  • Level 3 Communications (Nasdaq: LVLT)
  • Summer Infant (Nasdaq: SUMR)

Some of these names might surprise you. For example, aluminum leader Alcoa reported profits of $0.24 a share yesterday because aluminum prices had risen significantly. That was well ahead of the $0.18 analysts were expecting, but there was a word of caution, too, because the company expects China's aluminum consumption to grow "only" 15% this year compared with 21% last year. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold.

That could be the case with Summer Infant, which isn't as familiar but makes products geared toward babies and toddlers. When Bed Bath & Beyond bought similarly situated buybuy Baby from a co-chairman's son, I was skeptical that it was little more than a bailout at shareholders' expense. That still might be the case, but it has proven to be a growing business for the home goods retailer nonetheless. While it doesn't break out the revenues from each of its business lines, Bed Bath & Beyond has expanded the number of stores from the original eight to 42 today.

Because some of the 170,000-plus CAPS members have chosen 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?
Using its ability to generate strong cash flows, diversified giant 3M has been acquiring a number of companies, including Winterthur, Cogent Systems, and most recently Nida-Core. In its efforts to stay ahead of rivals Avery Dennison and DuPont, 3M is using its pocketbook to ensure it's a leader in innovation.

But beyond just buying growth, 3M is also pursuing organic opportunities to increase sales by 7% to 8% a year, roughly double what it has been doing so far. Analysts are skeptical, suggesting it's not an easy path to grow sales and pointing out that acquisitions create financial risk.

CAPS All-Star mrindependent says that considering the stability a company like 3M offers, its current price looks good.

I also note that valuation is attractive given the stability and strength of this company, which also has the proven ability to continue growing sales.

Almost 97% of the more than 4,200 CAPS members rating the conglomerate expect it to outperform the broad market averages, but you can tell us on the 3M CAPS page whether or not you agree.

Dirt cheap?
The Food and Drug Administration is proposing that graphic warning labels including pictures of tracheotomy patients, bodies on a slab at the morgue, and emaciated cancer patients be printed on cigarette packs. Canada is already doing it.

Cigarette makers like Altria (NYSE: MO), RJ Reynolds, and British American Tobacco already face challenges from taxes, and British American Tobacco is saying it expects Japan's cigarette market to decline by about 20% in 2011 because that country imposed a record tax hike. At one time, foreign markets were viewed as friendlier to cigarette makers, but no more.

CAPS member shanelofgren believes British American Tobacco's ability to cut costs will help shield it.

Their history of sales growth, margin growth, and cash flow growth is very encouraging. Their commitment to cutting costs and redesigning their global supply chain seems to be driving this margin growth and it seems that they have further improvements they can make. As for growth in sales, they are unveiling new brands but their main growth driver seems to be the simple fact of their presence in many growing economies.

On the level
Level 3 Communications isn't the only one grousing over NBC Universal's purchase by cable operator Comcast. DirecTV, Verizon, and AT&T are all scrutinizing the impact the purchase will have on the industry. With many hands stirring the pot, it could take a long time before that soup gets made.

But the telecom services provider is also doing the work necessary to ensure it remains competitive, such as stealing business from Netflix away from rival Akamai Technologies. Those types of moves, plus improved products, mean CAPS members clint47283 and edwatki look at Level 3 as the leading contender to come out ahead.

A great opportunity for you
Investor sentiment suggests these four-star investments still seem to be on their way to five-star greatness, but 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.

3M is a Motley Fool Inside Value recommendation. Akamai Technologies is a Motley Fool Rule Breakers selection. Bed Bath & Beyond and Netflix are Motley Fool Stock Advisor picks. The Fool owns shares of Altria Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

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