From T. Slivnik & Associates:
On most Unix-based operating systems, filesystems to be mounted at system startup are listed in the /etc/fstab file. The format of this file is described in the fstab(5) man page. While Mac OS X supports /etc/fstab, the preferred method on Mac OS X for specifying filesystems to be mounted at startup is NefInfo. Whilst Mac OS X will automatically mount all filesystems listed in NetInfo and UFS and HFS filesystems listed in /etc/fstab at startup, it will ignore the lines in /etc/fstab referring to NFS filesystems, not mounting them, despite the fact that the mount_nfs(8) man page states otherwise. MountNFS is a little startup item which restores the missing functionality. Once this item is installed, NFS filesystems listed in /etc/fstab will be automatically mounted at system startup.