Snow leopard server: use a NAS volume as share point
Mac OS X Server does allow the resharing of AFP mounts but not SMB/CIFS mounts. You can however get around it by using a symlink (ln -s /Volumes/Volume_1 /SOME/PATH) and share /SOME/PATH. While both options allow it to work it's not recommended (permissions, resource fork handling, max file size, etc. may cause hard to debug issues).
Alternatively on the command line you can use sharing (eg. sudo sharing -a path -s shareflags)