Parallel Port Programming - Describes the a fairly portable way to do parallel port programming. Presented in a simple, painless fashion. (cscene.org) - http://www.gmonline.demon.co.uk/cscene/CS4/CS4-02.html
Interfacing the PC - Free online tutorials about interfacing the Parallel (SPP, EPP & ECP), RS-232/Serial Ports and AT Keyboard. A detailed document on Interrupts (IRQ's) is included. Most documents available in PDF. - http://www.beyondlogic.org/