Here's an option that's still unfamiliar to many people but that has been growing in popularity: Lending money on a peer-to-peer basis. A major website for this is, where investors have earned returns in the neighborhood of 4% or more annually. You'll be lending money to fellow individuals who have had trouble borrowing money through other avenues, and you can spread your dollars across many such folks to reduce the risk.
The reason to make use or virality, the ease in spreading and sharing, is however a double-edged sword. We cannot forget that in this type of campaign, a large part of the control falls into the hands of the users, and we risk the message being misinterpreted or parodied. On the other hand, a successful viral campaign can work miracles for your brand’s results.