fam++ is a C++ wrapper for fam, which uses imon or DNotify (Linux 2.4.x) to inform it when inodes change (the net effect being that applications can register interest in a file, and have events send to the application when the file changes). Fam++ also integrates with gdk and Loki to make creation of C++ GTK+/GNOME apps simpler.
FerrisSambaModule is a VFS module for Samba 3.x which allows it to provide shares which use libferris as a data source. Thus, anything libferris can access can be shared as a filesystem via Samba, including LDAP, PostgreSQL, XML files, sleepycat dbXML database, evolution mail client, and queries against libferris' various indexes.
fuselagefs consists of a C++ wrapper class for FUSE called Fuselagefs, as well as Delegatefs, which is a Fuselagefs subclass that delegates all operations to an underlying base filesystem. With Delegatefs, you can expose dir1 at mountpoint dir2 very easily as a FUSE filesystem. Subclasses of Delegatefs can then be created, which add a little extra functionality to the delegation operation but rely on the parent class to perform the work and return errors to FUSE in an appropriate manner. An example subclass is petardfs.