BigDoor Media, which builds white-label virtual goods systems for publishers, has raised $5 million in a funding round. BigDoor’s platform lets third-party sites and apps add a host of what it describes as “game mechanics,”  including a virtual goods marketplace, badges and rewards, so that they can boost engagement (and diversify their revenue beyond advertising). The platform has been used by TV fan community Buddy TV, which lets its visitors send TV show-related gifts, like a rose from The Bachelor, or a kiss from Meredith (NYSE: MDP) on Grey’s Anatomy; the Cheezburger Network, known for sites like I Can Has Cheezburger?, is also testing it so that visitors can earn virtual trophies when they add content or vote.

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BigDoor takes a cut of virtual goods sales and also charges a fee based on usage of its API. The funding round was led by Foundry Group. More details on the company’s blog and in the release.