IPFS (Inter-planetary file system) has a sister protocol called Filecoin, Filecoin is used to pay miners (nodes that store data) using a novel value-for-data mechanism called Bitswap. Cryptocurrency makes sense here: its value transfer is fast and it allows for micropayments to pay for every correlated byte of storage. Filecoin is currently in development, but IPFS is already available to use. IPFS commands are currently free and the miners currently storing data are doing so out of their love of the network. Eventually, all uploads and downloads will require Filecoin.
IPFS borrows from Git's version-control model to version all data. Git used a DAG to model versions of data and IPFS uses it to give structure to the entire system. Users can see the version history of their data (or any data to which they have decrypted access).
So, IPFS takes the best ideas from Git, DHTs, SFS, BitTorrent, and Bitcoin and combines them to create a decentralized data-storage network, IPFS hopes to one day replace the HTTP:// protocol of the Web with IPFS://, but they can work in unison as well in several ways the we'll get into when we begin taking about implementation.
Ethereum Swarm
Ethereum is working to build a general-purpose (turing-complete) blockchain computing language, including decentralized storage.
Storj
Stroj has garnered a lot of hype lately; it has pre-mined a lot of StorJcoins and has made some pretty designs.
Maidsage
Maidsafe, like Ethereum, is trying to do many things. They aren't using proff-of-work and aim to create a decenteralized platform for computing, storage, and currency.
