PySamba is a Python library that provides a full wrapper for the Samba CLI library provided with samba-3.0.24. It includes a Python module that hides the complexity of the lower layer (SMB), providing high-level commands like Mkdir or DiskAvail. PySamba allows the developer to interface to any samba-capable device much like Python's ftplib does.
Proxy filesystem for FUSE is an implmentation of a filesystem that resolves symlinks and displays them as real folders as well as doing a few more things. For example, it is possible to point a folder or a single file at a file in the user's home directory. Also, it is possible to hide files and directories from the folder listing.
Magma is an experimental network filesystem for Linux and BSD kernels based on a distributed hash table. Each object stored is called a "flare" and is managed using its SHA1 hash key. Flares can be moved as opaque objects from node to node and requests can be proxied through the network transparently to the user. Its goals are scalability, redundancy, data availability, compliance with POSIX, and basic encryption on the user side.
Embedded File System (EFS) is a C++ library that allows you to create virtual file system in a single file. It can be useful when you need to create really big number of small files, as it is still fast even when you have millions of files. An encryption layer could be easily added for security.