MUSE is an implementation of a "multiple mounts merging" filesystem.
It's something like unionfs, but it allows writing to all the underlying filesystems at the same time.
It is suitable for convenient unification of large disk arrays when fault-tolerance is not the top priority.
posixovl is a FUSE filesystem that provides POSIX functionality (UNIX-style permissions, ownership, special files) for filesystems that do not have such, for example vfat. It is a modern equivalent of the UMSDOS filesystem.
Cmdfs is a FUSE virtual filesystem that applies an arbitrary filter command to selected files in a source directory tree to create the destination files.
It includes configurable caching and monitoring of the source tree to limit CPU use and prefetch data.
DemuxFS is a filesystem which demultiplexes MPEG-2 transport streams, exposing tables and their members as directories and files. It includes support for the DSM-CC protocols and provides access to audio, video, and caption streams through FIFOs.
dumbofs allows you to view databases and tables from a PostgreSQL server as regular directories and files. It also allows the creation of special "search folders" which contain database records matching certain given criteria.
ccgfs is a transport-agnostic network filesystem using FUSE. Transport is arranged by helper programs, such as SSH. The PUSH transport mode acts like a "reverse" NFS and makes it possible to export a filesystem from a firewalled host without defeating the security model.