Some CUPS backends. See descriptions below

 Name                    Last modified       Size  Description

 Parent Directory        10-Jul-2003 09:09      -  
 print-to-disk           05-Apr-2003 00:02    14k  
 smb-helper              05-Apr-2003 00:10     2k  
 helios                  05-Apr-2003 16:57     5k  
 pap                     08-Jan-2004 16:38    10k  
 fax                     20-Feb-2004 11:53     3k  

helios

   This backend can be used to print to Helios Ethershare queues, so one
   can use IPP with Helios

pap

   Yet another backend that can talk to AppleTalk devices. As far as I know
   this is the only one in the wild (except the one from Apple included in 
   MacOS X), that can deal with different zones, fetch the "Product name" from
   printers of type LaserWriter and sends additional form feeds to DeskWriters

print-to-disk

   A backend to print into the file system. Doesn't overwrite already existing
   files with the same name, can drive ghostscript with custom options (own
   hotfolder scheme similar to distiller's one), calls post-processing apps and
   can be enhanced via "actionscripts" (some sort of a plug-in mechanism)

smb-helper

   Helps finding windows printer shares by NMB lookups