GFS
(Sistina) is fault tolerant and distributed. It is also both a cluster and a journalling file system.

GPFS
GPFS, under development at IBM, it's a high performance parallel, scalable file system for clusters.

InterMezzo
InterMezzo is a distributed file system with a focus on high availability, offering various features like disconnected operation and automatic recovery from network outages.

Lustre
Lustre is a novel storage and file system architecture that aims at building a next-generation cluster file system, to service clusters with 10,000s of nodes, petabytes of storage, and move 100s of GB/sec, as well as offering security and management.

OpenAFS
Under development at IBM's Linux Technology Center.

OpenGFS
OpenGFS free version of GFS, fault tolertant cluster and journalling file system.

PVFS
PVFS developed at Clemson University's Parallel Architecture Research Lab, related to the Beowulf Project.

IBRIX
IBRIX Fusion allows enterprise system administrators to build file systems that can scale to up to 16 petabytes of capacity in a single namespace, and provide up to 1 terabyte/sec of aggregate I/O throughput performance, independently and non-disruptively as the demands of the enterprise grow.