Welcome back to Baby Breakerdom! This week's quest to uncover budding Rule Breakers finds investors seeking the Limelight and peeking under the Zillow.

First up this week is Limelight, a start-up that's taking on established players in the content-delivery networking market, including leader and Motley Fool Rule Breakers selection Akamai Technologies (NASDAQ:AKAM). Now Limelight has $130 million more to use in its quest for digital dominance.

Goldman Sachs Capital Partners led the round, which brings Limelight's total external funding to $145 million. How big of a threat is this Baby Breaker to Akamai and peers VitalStream (NASDAQ:VSTH) and SAVVIS (NASDAQ:SVVS)? That's hard to tell, but Limelight Chief Strategy Officer Mike Gordon said in an interview yesterday that the company's network is optimized for the sorts of very large files that come with streaming media and music and video downloads. A growing customer list, including YouTube and Microsoft's Xbox Live, bears witness to that claim.

What's more, Gordon says, Limelight plans to use some of the funding to beef up its already-expansive network. But don't expect to see Limelight servers in more locations. Instead, Gordon says, the company operates out of several data centers around the globe, each hosting hundreds of servers and dozens of networks. Akamai, which Gordon refers to as a "first-generation" CDN, takes a different approach by serving thousands of global sites with a handful of servers at each site.

Which approach will win out? Neither my crystal ball nor my magic 8-ball will say. But either way, the CDN market is experiencing a massive growth wave that may lift every public firm in its wake. Just don't expect Limelight to join the IPO party soon: CEO Bill Rinehart is banned from serving as an officer or director of a public company until next summer. The SEC accused Rinehart -- a former sales VP with Critical Path -- of fraud in 2002, but settled the case immediately, without asking him to admit guilt.

Next up is Zillow, a remarkably useful site that allows users to see the appraised value of their homes, then compare that value with similar dwellings. It's what many call a "Web 2.0" service, in that it aggregates data from multiple sources to produce unique content. Some, including our own David Gardner, have wondered whether the technology behind Zillow will democratize the real estate market in the same way that founder Richard Barton's last company, Expedia (NASDAQ:EXPE), helped to forever change travel-planning.

Investors seem to think the idea is Rule Breaking enough. VentureWire reports that Zillow raised $25 million in second-round financing from Par Capital Management, Benchmark Capital, and Technology Crossover Ventures, increasing its total raised to $57 million.

That's all for now. See you back here next Friday, when we continue our quest to find the next ultimate growth stock.

For more Rule Breaking Foolishness:

High tech. Biotech. Nanotech. Any tech. David Gardner and his Foolish band of analysts cover it all for Motley Fool Rule Breakers , and they've unearthed four multibagger stocks in less than two years as a result. Akamai is one. Who are the other three? Try the service free for 30 days and find out.

XM is another Rule Breaker selection, while Microsoft is anInside Valuerecommendation.

Fool contributor Tim Beyers owns shares of Akamai. You can find out what other stocks he owns by checking Tim's Fool profile . The Motley Fool has an ironclad disclosure policy .