Maybe it was mentioned before, but anyway here is a really fine controller web site with heavy Linux emphasis; http://www.beyondlogic.org/ This area of Linux is really taking off. The USB interface for controllers seems to offer outstanding "user mode" improvements over the standard parallel and serial port 8 bit interrupt control "real mode." Great tutorials are provided, and great cheap (even prototyping) USB controller hardware is reviewed. Several USB/serial,parallel converters are described. Lots of Linux controller software is also available. The serial port UART is still great for the DTE end, but the host side should certainly use USB.