XFS is SGI's FileSystem designed from the ground up for massive filesystems and high performance, especially on large multi processor configurations. SGI have ported the original IRIX code to Linux, and it has been merged into the 2.6 tree.
It has some very interesting features, like dedicated high performance I/O areas, allowing you to dedicate part of your disk to files that you want very low latency to access, for example video files you are currently editing. Sadly, most of the really neat stuff (guarenteed rate I/O, realtime subvolumes) is still only available IRIX.
Regular snapshots for the 2.4 series are available from http://oss.sgi.com.