RFind indexes the filenames of a given directory, and allows you to quickly search this index with regular expressions. Search-on-typing with more than 500,000 indexed filenames is easily possible. This tool attempts to be very configurable so that it can be useful to everyone. It features hierarchically presented search results, search-on-typing, and the ability to define rules to execute on mouse click.
Earth allows you to find files across a large network of machines and track disk usage in real time. It consists of a daemon that indexes filesystems in real time and reports all the changes back to a central database. This can then be queried through a simple Web interface. Think of it like Spotlight or Beagle, but operating system-independent with a central database for multiple machines. Earth is initially focused on managing the explosion of data that occurs in digital visual effects work.
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.
libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. You can use this for viewing and editing files inside guests, scripting changes to VMs, monitoring disk used/free statistics, P2V, V2V, performing partial backups, cloning VMs, and much more. libguestfs can access nearly any type of filesystem including: all known types of Linux filesystem (ext2/3/4, XFS, btrfs, etc.), any Windows filesystem (VFAT and NTFS), any Mac OS X and BSD filesystems, LVM2 volumes, MBR and GPT disk partitions, raw disks, qcow2, CD and DVD ISO images, SD cards, and dozens more. libguestfs doesn't need root permissions.