ALDL pinout and data stream on corvette?

[Steve=Ravet%Prj=Eng%PCPD=Hou at bangate.compaq.com]

Howdy

I'd like some information on the ALDL connector for the Corvette.  The ALDL is 
the diagnostic connector on computer controlled GM cars that provides 
diagnostic information to a computer.  Info such as rpm, injector duty cycle, 
EGO, timing, etc.  I know it's possible to hook a PC up to this and collect 
info, because there is a company that sells just such a product (in addition 
to GM, of course).  I'd like to write my own software to run on a laptop to do 
this.  What I don't know is the pin out of this connector, and the format of 
the data stream.  If anyone can tell me this, or point me in the right 
direction, I'd be most appreciative.

thanks
--steve