EncFS is an encrypted pass-through filesystem which runs in userspace on Linux (using the FUSE kernel module). Similar in design to CFS and other pass-through filesystems, all data is encrypted and stored in the underlying filesystem. Unlike loopback filesystems, there is no predetermined or pre-allocated filesystem size.
GNU xorriso creates, loads, manipulates, and writes ISO 9660 filesystem images with Rock Ridge extensions. Files can be copied in and out. The session results get written to optical media or to filesystem objects. Rather than needing external tools for ISO 9660 production and CD/DVD/BD burning, it is a static compilation of libburnia-project.org. Thus GNU xorriso depends only on fundamental operating system facilities.
libferris is a virtual filesystem that exposes hierarchical data of all kinds through a common C++ interface. Access to data is performed using C++ IOStreams and metadata is available as key-value pairs through the Extended Attributes (EA) interface. Rich support for filesystem indexing is included to provide timely search results for well into millions of files. Ferris uses a plugin API to handle a large range of data sources, metadata, and index and search strategies. Filesystems include file:// with monitoring, XML (mount an XML file as a filesystem), relational databases, ISAM databases (Berkeley db, tdb, gdbm, eet et al), xmldb, LDAP, Applications (Evolution, Firefox, Emacs), HTTP, FTP, sockets, and RDF (from XML, binary, soprano). EA generators include image, audio, and animation decoders.
BleachBit deletes junk to recover disk space and maintain privacy. It rids your system of old junk including cache, Internet history, temporary files, unused locale files (better than localepurge), logs, and cookies. Designed for Linux systems, it wipes clean 50 applications including Adobe Reader, Bash, Firefox, Flash, OpenOffice.org, Opera, Real Player, Skype, and more. It shreds files so that they cannot be recovered, and it wipes free disk space to hide insecurely deleted files. It offers both a simple PyGTK GUI and a command line interface for automation.
Chiron FS is a FUSE based filesystem that implements replication at the filesystem level like RAID 1 does at the device level. The replicated filesystem may be of any kind you want; the only requisite is that you mount it. There is no need for special configuration files; the setup is as simple as one mount command (or one line in fstab).
Einarc is a unified storage RAID command line interface and an API that provides management for various hardware/software RAID devices, uniting them all in a single paradigm. Einarc works as a translator that makes it possible for a user to control all these devices using simple terms like "physical disc", "logical disc", "adapter", etc., while transparently converting these requests to proprietary RAID paradigms.
Shake is a defragmenter that runs in user-space while the system is in use (for now, on GNU/Linux only), without the need to patch the kernel, and without the need to patch the kernel. Unlike xfs_fsr, it only uses functions common to all filesystems. It aims to evaluate the cost of fragmentation based on criteria such as fragment number, distance from "friends" (by default, a group of files used at the same time), file age (rewriting old files allow the filesystem to reclaim free space), file size, and number of "crumbs" (very small fragments that force the head to move repetetively). A Python module that parses the output of the verbose mode is included.