So you want to learn more about EFI theory, ECUs, or just stuff in general. This is intended to be a place to put links to stuff worth reading.

Hon Data's website - tons of good information, much of it very aplicable considering they use stock ECUs as the base for their standalone

http://www.diy-efi.org - started out with a heavy slant towards domestics but has a WEALTH of good knowledge and tons of very smart individuals on the mailing list

http://www.efi-tuning.org - a site dedicated to tuning mostly GM and Bosch (BMW,etc.) ECUs

http://www.eci-multi.org - PGMFI's equivalent for DSMs.

http://www.sdsefi.com - a commercial vendor of standalone engine management systems that has a tech section with every article worth reading twice

http://www.howstuffworks.com - a great site with many quality articles on automotive related topics, as well as a ton of information on the scientific theory behind the operation of things. Tons of pictures, fascinating redaing.

http://www.bgsoflex.com/megasquirt.html - The Mega Squirt? is a homebrew DIY fuel injection computer that is pretty well documented and has full schematic.

http://www.bgsoflex.com/mjl/mjl_edis.html - Mega Jolt? is a prtially complete system for controlling ford EDIS modules

http://home.comcast.net/~tjhafner/MegaSpark.html - Mega Spark? is a DIY system for controlling spark standalone using a 6AL or similar to drive the spark itself.