An Alphabet of File Systems

AFS
Andrew File System
DFS
Disc Filing System
FFS
Fast File System (a particular breed of UFS)
GFS
Global File System
HFS
Hierarchical File System
JFS
Journaled File System
LFS
Log-Structured File System
MFS
Macintosh File System
NFS
Network File System
UFS
Unix File System
XFS
XFS (it's not clear that the X stands for anything; it just sounds cool)
ZFS
Zettabyte File System