Perkeep (née Camlistore) is a set of open source formats, protocols, and software for modeling, storing, searching, sharing and synchronizing data in the post-PC era. Data may be files or objects, tweets or 5TB videos, and you can access it via a phone, browser or FUSE filesystem.
Perkeep is under active development. If you’re a programmer or fairly technical, you can probably get it up and running and get some utility out of it. Many bits and pieces are actively being developed, so be prepared for bugs and unfinished features.