CUPS? It stands for Common Unix Printing System and is an open source application. From the CUPS web site:
CUPS is the software you use to print from applications like the web browser you are using to read this page. It converts the page descriptions produced by your application (put a paragraph here, draw a line there, and so forth) into something your printer can understand and then sends the information to the printer for printing.
Now, since every printer manufacturer does things differently, printing can be very complicated. CUPS does its best to hide this from you and your application so that you can concentrate on printing and less on how to print. Generally, the only time you need to know anything about your printer is when you use it for the first time, and even then CUPS can often figure things out on its own.
CUPS is distributed with many Linux distributions and has been bundled with Mac OS X since the Jaguar edition (10.2). Apple had initially attempted to create it's own printer system from scratch, but then shortly adopted CUPS. This past February Apple quietly hired the creator of CUPS and bought the code, but continues to make it available as an open source project. The announcement was just made on the CUPS web site July 11.
Hopefully, Apple will continue to keep CUPS open. This should be good for CUPS, since it assures financial backing for the project. There was a commercial version which is no longer available, although the reference book can still be bought but they are not accepting any orders while they move from Maryland to California. It is the best system on Linux for managing printers which is done via web browser administrative interface. It is what is used on our Linux file and print server which runs ClarkConnect.