Here are some links I've collected recently. Please feel free to add your own favorite MR2 links to the thread!
Matti Kalalahti's Tech Site -- http://www.kalalahti.com/tm_index.html
1986-1989 MR2 MKI Supercharged Registry -- http://www.mr2sc.com
Automotive main page -- http://www.kalalahti.com/tm_index.html
RPM Lab - MR2 MK1 Design and Engineering -- http://www.rpmlab.com/design.html
aw11mr2's Photo Gallery -- http://www.pbase.com/aw11mr2/root&page=all
Toyota MR2 Wiki and FAQ -- http://mr2wiki.com/MKI/DIY
MR2MK1Club -- http://www.mr2mk1club.com/_newsite/index.php?currPage=mr2mk1
MR2 Mk1 World Community - MR2 MK1 Club North East Region -- http://www.michael-sheavills.co.uk
MR2 Nutt -- http://www.mr2nutt.com
85-89 Toyota Mr2 Parts at Andy's Auto Sport -- http://www.andysautosport.com/toyota/1985_1989_mr2/
Japanese:
AW OASIS -- http://page.freett.com/brp2/main.html
Forest Rice -- http://www5d.biglobe.ne.jp/~fos4416/
HIGH-GEARed -- http://nabeck.web.fc2.com
German:
Toasted Online MR2 -- http://mr2.at.tt
Lots of tech info on 4A-GZE:
http://www.mr2.net
Pretty cool MR2 write-ups
http://www.toyoland.com/mr2-1992-toyota.html
I realize this is for MR2's, and Matti's site has been a fantastic source of info in the past, but two sites that should be added are Bill Sherwoods and club 4ag. Neither one is centered on the MR2, or even goes indepth on the subject of MR2's, but they contain a great source of info on the 4AGE.
www.billzilla.org (http://www.billzilla.org)
www.club4ag.com (http://www.club4ag.com)
Subject updated :D