http://furquim.org/chironfs/
ChironFS is a fuse based filesystem that supports multiple backends. Writes are written to multiple hosts, reads come from a single host. It removes single points of failure and provides real time duplication / backup.
http://dav.sourceforge.net/
The equivalent of sshfs but for webdav. Mount webdav shares as local filesystems using filesystem in userspace (fuse).
