Here's a list of websites that have been useful to me. There is a lot of very technical web sites here doing with modifying the PCM and building circuits to get trouble codes from both OBDI and OBDII vehicles. Do so at your own risk.
http://www.megasquirt.info <-- Home page for MegaSquirt fuel injection system. All information to build the MegaSquirt is found here.
http://www.msefi.com <-- Forum filled with information about the MegaSquirt fuel injection system and other components.
http://www.badbowtie.com <-- Website for Chevrolet fans, some import & ford humor as well, check it out!
http://www.fierolt1.com <-- LT1 powered Fiero's
http://www.blacky.co.nz/free/index.htm <-- OBD-II 100% software interface, pull trouble codes
http://www.elmelectronics.com/index.html <-- maker of OBD-II interface chip
http://www.obdii.com <-- Dedicated to helping the home technician understand and use OBD-II technology.
http://www.diy-efi.org <-- Good place to search for hard to diagnose computer problems, and advanced fuel injection systems.
http://www.up22.com <-- Fiberglass for almost ANY vehicle, very well priced too!
http://www.fuelinjection.com/portinj.html <-- History of GM Port Injection, lots of info too.
http://www.mortec.com <-- Casting numbers for any Chevrolet block, head, or crank. Also lots of information for tuning Holley Carbs.
http://www.charm.net/~mchaney/optisprk/optisprk.htm <-- Very useful information about the Optispark distributor.
http://para.noid.org/~muttvette/opti.html <-- What you need to know about Optispark changes from 92 to 97.
http://www.coatesengine.com <-- Very interesting website, an engine with a rotary valve, no lifters, no pushrods, no CAM! Check it out!
http://www.lt1intake.com <-- Info on modifying an LT1 intake to use with a standard distributor, on early SBC blocks.
http://www.fatmanfab.com <-- Make aftermarket suspension and steering components, as well as lowering kits and bags for many vehicles.