Have you ever owned a tweener?

A tweener, dear Fool, is like your pal Chuck. Still a great athlete, Chuck no longer rules the hardwood with his 40-inch vertical leap. He's become what we sports addicts call a gamer. He passes more. He's developed a nice shot from the corner. And though he doesn't dunk as much, or as spectacularly, as he once did, Chuck is still a force in the paint.

What we fans don't know is how long Chuck will be in the starting line-up. Chiseled veteran Abe has a wicked hook shot that won't quit. And Larry, the little guard whose hip shaking moves smoke defenders, has the makings of a future superstar. Both are vying to cut into Chuck's minutes on the floor.

In Foolish parlance: Chuck is a tweener, Abe is a Rule Maker, and Larry is a Rule Breaker.

Growing up is hard to do
The stock market has plenty of Chucks. They'll either create billion-dollar fortunes as they come to dominate industries, as Cisco, Microsoft, and Google have, or they'll be destroyed in the process, as Gateway was.

Therein lies the problem. Investing in tweeners can be dangerous and  exceptionally profitable -- the trick is picking your winners well, as David Gardner has. He produced nine years of 20% average returns hunting for misunderstood multibaggers in the making. His team at Motley Fool Rule Breakers continues the tradition today.

Let's have the list
You, too, can join in the effort, thanks to Motley Fool CAPS. Each week, we'll use the database to find three-star stocks that are expected to boost earnings by at least 15% annually over the next five years. Here's today's list:

Company

CAPS Rating

5-Year Growth Estimate

Starent Networks (NASDAQ:STAR)

***

57.5%

Limelight Networks (NASDAQ:LLNW)

***

35%

Blue Coat Systems (NASDAQ:BCSI)

***

26.3%

CNET Networks (NASDAQ:CNET)

***

16.3%

Knight Capital (NASDAQ:NITE)

***

15%

Sources: Motley Fool CAPS, Yahoo! Finance.

Bear in mind that this isn't a list of recommendations. Instead, I offer these stocks as candidates for further research. But of these five, it's CNET that interests me most.

But I must admit, I'm biased. CNET was picked for Rule Breakers by my Foolish compadre Rick Munarriz, and I've long agreed with his thesis. In short, CNET's Web properties are some of the best in the business and, as such, should fuel years of growth.

Then there's the valuation. CNET trades for just 6.5 times its expected 2007 earnings -- pretty cheap for a company that expects double-digit income growth to 2012.

Others aren't much for the business or the valuation. Instead, they're waiting on a buyout. One of my favorite Fools, Dan Rubin, known in these parts as TMFHollywoodDan, explains:

I am deeply skeptical of this business model, which includes CNET owning 82,000 promising domain names and planning to max [them] all out. I'd love to see them drop a ton of them, trim their staff, and focus on the 10-25 best ones. I have a strong gut feeling this one gets bought out. It's part of my Quadruple Media Buyout Package-Netflix, TiVo, DreamWorks, CNET.

Do you agree? Disagree? Do your own due diligence and then check in with thousands of other investors at CAPS. And, if you'd like, add your own commentary. You'll be helping your fellow Fools and testing your ideas at the same time. Click here to get started now. The service is 100% free.

See you back here next week for five more growth stocks stuck in the middle.

How great is growth? More than 10 stocks in the market-beating Rule Breakers portfolio, which includes CNET, have at least doubled. Discover their identities with a 30-day guest pass to the service. There's no obligation to subscribe. 

Microsoft is an Inside Value pick.

Tim Beyers, who is ranked 10,238 out of more than 65,000 participants in CAPS, is a regular contributor to Fool.com and Rule Breakers. Tim didn't own shares in any of the companies mentioned in this article at the time of publication. Click here for Tim's portfolio and here for his latest blog commentary. The Motley Fool's disclosure policy prefers a little less conversation and a little more action.