At work we have a (necessarily) complicated printing system for the student computer labs. Mac and PC workstations print via LPR to Windows print queues. On the Windows Server 2003 box Pcounter takes control of releasing jobs and charging student/faculty accounts for the prints.
Most of these queues feed the jobs to various laser printers throughout the building, but several of our print queues are for wide format inkjet printers, so the queues pass the files off to other 2003 Server boxes running ColorBurst RIP software. ColorBurst has its own printer port (CPT1: ColorBurst Port Monitor), so all incoming print jobs are handled by a Windows print queue using this port. ColorBurst runs as an application, not as a service, and it unfortunately crashes quite regularly.