APR based virtual file system library and modules for read/write access to gzip, bzip, tar, cpio, iso and zip archives.
Mudslide provides an encrypted file system to any operating system that can mount a webdav server. Mudslide works with Linux, OS X, and Windows. Mudslide is built upon http://jakarta.apache.org/slide/ and the encryption libraries packaged with Java.
ZFS is a system of automatically replicating file servers closely resembling CODA.