Lighttpd

One of the main drawbacks of MogileFS is it must be application aware. However, if the application is a webserver, it could effectively provide transparent file access across N number of servers (MogileFS should scale horizontally quite well)

This might not be useful for PHP/etc. apps, since those would have no concept of the "virtual" filesystem in place, however for hosting binaries/media files/etc, this could provide a neat solution to replace the need for NFS (and provide probably more thoroughput, redundancy, etc.)

It would allow for the files the webserver accesses to be completely transparent in the event of a server loss (as long as each file is being replicated at least 2x in the storage cluster)

More info on MogileFS here: http://danga.com/mogilefs/
(Looks like it already has ties in to Lighty, possibly for its GET requests: see Mogstored::HTTPServer::Lighttpd)