This is a new release of squashfs, a highly compressed read-only filesystem for Linux. Squashfs compresses both files, inodes and directories, and supports block sizes up to 64K for greater compression. It is implemented as a kernel module under VFS.
Squashfs 3.1 has some major improvements to the squashfs-tools, a couple of major bug fixes, lots of small improvements/bug fixes, and new kernel patches.
You can download squashfs from this page: