[B}AIM[/b] is a Global Trade Organization for Automatic Identification and Data Collection . The site has good information and lots of links.
Are you looking for the diagrams for a keyboard wedge (to connect a scanner device to a computer via the keyboard port? Or one that connects to the LPT or serial ports and the decoding is handled by software on the PC? If you are looking for information on the latter, go to Radio Shack and pick up a CueCat