OpenPrinting has lots of resources to help with printing under free operating systems like GNU/Linux and the BSDs or under commercial UNIX-like systems such as Solaris and OS X.

• Foomatic
  Foomatic is a database-driven system for integrating free software printer drivers with common spoolers under Unix.

• CUPS
  CUPS is the recommended spooler especially for printing in a Linux environment. Default spooler under OS X
• LPRng
  LPRng is a newer implementation of an LPD-protocol based print spooler done with the goal of a high security level.
• PPR
  PPR is a Postscript-centric print spooler written by and for Trinity College
• CPS
  CPS (Coherent Printing System) is a Foomatic/GhostScript-based print spooling system
• PDQ
  Is a good printing system for non-networked setups
• GNUlpr
  A (formerly) HP-funded project by VA Linux to provide better support for printing.

• Gutenprint
  Gutenprint (formerly Gimp-Print) provides the highest quality free printer drivers around.
• HPLIP
  HP Linux Imaging & Printing, is HP’s free drivers for their printers and multi-function devices.
• OMNI
  The Omni printer driver provides support for over 450 printers using the Ghostscript framework.
• GhostScript
  This is the PostScript interpreter used by Unix and alike operating systems to be able to print on non-PostScript printers.
• ESP GhostScript
  This is an enhanced version of GNU GhostScript published by Easy Software Products
• IJS
  A plug-in interface which allows to add new drivers to GhostScript without needing to patch and recompile it.