LUFS is a hybrid userspace filesystem framework supporting many "exotic" filesystems (localfs, sshfs, ftpfs, httpfs, socketfs, freenetfs, and nutellafs) transparently for any application. It can be regarded as doing the same job as the VFS (virtual filesystem switch) in the kernel: it is a switch, distributing the filesystem calls to its supported filesystems. However, LUFS filesystems are implemented in userspace. This would be a drawback for local filesystems where the access speed is important, but proves to be a huge advantage for networked filesystems where the userland flexibility is most important.
Squashfs is a highly compressed read-only filesystem for Linux. It uses zlib to compress files, inodes, and directories. All blocks are packed to minimize the data overhead, and block sizes of between 4K and 1M are supported. It is intended to be used for archival use, for live CDs, and for embedded systems where low overhead is needed.