Fundable.org has recently been launched, and is based on an interesting concept that mixes the power of social networks with purchasing capital. Basically, Fundable allows groups of individuals to collectively purchase goods or services with the understanding that if not enough money is collected, all money is refunded.
Two examples that are currently active include an open source programmer who is willing to update and GPL his software for OS 10.4 if he can raise $100, and a tube amplifier maker who hopes to sell a batch of his custom product. Other examples from the site can be found here. There are several interesting ideas.
I am not sure how well this will do, as no transaction has yet been completed. However, I think it has potential.