Gfarm is a distributed filesystem, generally used for large scale cluster computing. It's implemented in userland, and can be mounted by FUSE. It utilizes locality of a file to access a data node, and supports Globus GSI for Wide Area Network. Users can explicitly control file replica location on Gfarm. Gfarm can be used as an alternative storage system to HDFS for Hadoop, Samba, MPI-IO, and GridFTP. Monitoring via ZABBIX and Ganglia is also supported.
bfsync is a file-synchronization tool that allows you to keep a collection of big files synchronized on many machines. It is built around a FuSE filesystem, so repositories can be mounted and the contents can be viewed and modified via the mount point. A collection of commands like commit/push/pull/put/get can be used to control bfsyncs behaviour, and trigger data / history transfers between machines. In addition to synchronizing files between many machines, bfsync can also be used to store backups.
SIMPLE-MTPFS (Simple Media Transfer Protocol FileSystem) is a file system for Linux (and other operating systems with a FUSE implementation, such as Mac OS X or FreeBSD) capable of operating on files on MTP devices attached via USB to local machine. It allows the end user to seamlessly interact with MTP device files.
GitFS is a fuse- and git-based remote filesystem with local cache for disconnected operation. It does periodic commits and pushes/pulls to keep a local shadow file system in sync with a remote repository. The filesystem should continue to work when you are disconnected. Merging after disconnected updates from multiple locations is left to git.