http://www.vfaq.com/TMO/ (good tuning page with links, using TMO logger)
http://www.roadraceengineering.com/SiteMap.htm (Complete site map of thier page, has tech, upgrades etc)
http://www.miata.net/garage/tirecalc.html (Tire size calculations)
http://www.plymouthlaser.com/safc.htm (install that SAFC into a 1g)
http://www.4g61t.org/phpBB2/viewtopic.php?p=85155&sid=512d3c5ba61500d7ff6dbfcd6af20162 (VERY helpful page on what each Mitsu ECU is for, using case numbers, scroll down a bit for a huge list)
http://www.sdsefi.com/tech.html This is a link from a standalone EFI system page, they make thier own low cost EFI setup for racing, but the author is VERY knowledgable about tuning, turbos, fabrication etc and has put togeather a tech section. There are some VERY good articles in here from basic to very fancy.
http://forums.evolutionm.net/showthread.php?t=262346&highlight=ams+bosch+044 Fuel pump flow rates, with some different layouts and setups, newer than the one from RRE.
http://www.inliners.org/tech/tech6.html This is a link to a great way to find electrical shorts.
http://www.fastcoolcars.com/hp_calculator.htm Nice, simple accurate hp calculator. Not all wheel drive specific, so awd guys may be slightly under rated on this one.
http://www.hotrodcoffeeshop.com/forum/viewtopic.php?t=72 Wiring diagrams
/edited for dead links, added some new links/