With some dedicated software and maybe a little hardware, you might be able to make a "wand" style bar-code reader from your parallel port. It is not very difficult. However, the design can be tough if you want to read some really fine pitch barcodes. The usualy system has some led and a phototransistor. By swiping the wand across the code it looks at the light/dark/light patterns and using a lookup table converts that to the proper digit. The width of the bars is determined by timing the light and dark areas. I built one a few years ago using a micro and parts out of a junk box and it worked pretty well.