I'm working on a proof of storage cryptocurrency. It's quorum based as opposed to blockchain based, which allows it to scale such that each node only needs to track log(n) transaction while maintaining a secure network and being able to be certain about the validity of incoming transactions. Storage is cheaper, faster, and more secure than centralized alternatives. There is also functional (but expensive) support for secure decentralized computing.

It's nearly in an alpha stage. www.siacoin.com