Note that all links should go to the relevant wiki-page. See SiteIndex. Ideally this should only contain links about too generic pages (eg. web forums that are too unorganized to be really useful, but still might worth a mention).
In ListsAndForums you can quickly compose a coctail which best suits your interest and time. You can find an IRC channel too, where you can talk to developers!!
[The best introduction to diy EFI] Motorola megasquirt specific, but 80% applies to any EFI system, you will see the differences
[Sourceforge Project Page] - Open Forums
[Sourceforge Homepage] - Sourceforge home page.
[CVS repository webview] - see the doc/
[UISP for Linux] - UISP Programmer code for Linux
[AVR gcc] - gcc compiler for AVR
Much info about engine management. http://www.diy-efi.org/
Site with nice tech info http://wwwrsphysse.anu.edu.au/~amh110/
A PowerPC controller based ECM: http://feynman.ee.ualberta.ca/~jasmith/mpc555/docs/fp3.antelecom.net/tbehrens/aems555/results.htm
[http://www.avrfreaks.net/phorum/read.php?f=5&i=2027&t=1989" avrfreaks forum thread about engine management (need registration)]
Efi332 is a very nice ECM system, it is a little laborsome though: http://www.diy-efi.org/efi332/equations/algorith.htm
Megasquirt is the prophet of affordable fuel injection. It is about the same cost and labor to build as msavr, although it has considerably less functionality and free resources for future updates. It is very respectable that Magnus could fit ignition to it (with some limitations). It has incredibly detailed documentation (most of it is general to suit most efi systems, like msavr) and numerable success stories. Lance's megamanual and Erik's megatune is widely used in MS-AVR land too.
Look in http://retro.co.za/efi/DIY_EFI/1995/archive68.txt for some unorganized (as typical with forums) intro about many parts (drivers, trigger-amplifiers, knock sensors, even processors) useful in engine management. Look for the MGP20N40CL and look around.
Alexei Pavlov published some engine logs: ftp://ftp.diy-efi.org/incoming/engine_log.txt
A realtime OS for AVR: RTOS: http://www.barello.net/
Forums that could benefit from a powerful engine management solution: