Established online ad firm Gorilla Nation is betting that there’s advertising life beyond the top 50 kids sites for marketers looking to expand their internet reach. The agency’s new GNkids division launched last month with the goal of becoming a vertical market aggregator of mid-tail web properties. In other words, the L.A.-based company is repping immersive ad opportunities on sites that host traffic of between one million and 15 million unique visitors per month.

Millsberry.com and Kidzworld.com are already signed as anchor clients. Millsberry, operated by food giant General Mills, is a lively virtual world that plays host to three million unique monthly visitors who spend an average of 41 minutes a day there. And this month, thanks to GNKids, the site is sporting third-party advertising for the first time.

There are a number of other high-quality kids websites not being considered in marketing plans, says Gorilla Nation president Brian Fitzgerald. And the idea behind aggregating advertising opportunities on these smaller sites is simple enough. By representing several at once, the new division can present partners with a portfolio of kids properties that have significant reach, highly targeted Comp indices and lower CPMs. Plus it can provide one-stop creative execution services to make for more efficient ad buys.

For marketing giants like Kellogg’s and Nintendo, it means reaching new audiences in a less cluttered environment than on Nick.com, Disney.com or Cartoonnetwork.com. And for smaller marketers that don’t have the budgets to launch campaigns on the big three, it opens up a cost-effective channel because it doesn’t involve creating a campaign for each site and managing multiple buys.

GNKids is in the process of adding new sites to its network, and Fitzgerald says the division is looking to partner with smaller online entertainment and consumer products brands in the vein of Kids’ WB! or The Doodlebops, which could be good news for entertainment players looking to build incremental income.

Kyle Fletcher, who’s been at Kidzworld.com for the past six years, is heading up the North American GNKids operation. HQ’d in Vancouver, Canada as VP of ad sales, Fletcher is moving upcoming marketing efforts beyond the standard banners and pop-ups that are still all the rage on the top 50 kids sites in the US. He’s looking at creating fully integrated branding opportunities that engage kid users. To that end, Fletcher is in the process of setting up an in-house creative and design team to provide clients with a one-stop shopping experience.