jamboolVirtual currency seems to be the way to get venture capitalists to part with their real currency.

Jambool said it has raised $5 million in a second round of funding for its virtual currency and payments platform, Social Gold, which has become a common way to monetize games and other apps on Facebook and MySpace.

It is by hundreds of applications on social networks and across the web. If you want to send someone a virtual rose on Facebook, you can carry out the transaction and pay for it without ever leaving the virtual gift app, thanks to SocialGold. Jambool launched the service in October.

Other virtual goods platform players include Twofish, LiveGamer, Offerpal, Peanut Labs and PlaySpan.

While virtual goods was barely getting traction in the U.S. market a year ago, it’s now one of the hottest parts of games and social networking.

The round was led by Seattle-based Madrona Venture Group and existing investor Bay Partners also participated in the round.

The company plans to use the money to accelerate product development and expand distribution. It already has customers such as Real Networks and distributions partners such as Super Rewards, which helps companies monetize apps through special offers.

Jambool is based in San Francisco and Seattle. It previoulsy raised $1 million from Hit Forge, Charles River Ventures and Bay Partners.