I'll start:
http://www.fordsix.com
http://www.hotrodinlines.com


Others?

The H.A.M.B has a great deal of inline interest, and a lot of our traffic comes as a result.

Tim

http://sohcsix.yuku.com/

http://www.hotsixes.com/forum/

These are truck and Nova sites but search for six cyl:

http://www.stovebolt.com/

http://www.stevesnovasite.com/

Pete

And not to forget:
http://www.jjinlines.com/
http://www.cdpautomachine.com/
http://www.hotsixes.com/
http://www.sixbangerparts.com/home/
http://www.stoveboltengineco.com/
http://www.12bolt.com/
http://autos.groups.yahoo.com/group/GM_Inline_6/
http://www.splitzmanifolds.com/
http://www.engineracing.com.br/pecasnacionais.html
http://t6racing.org/index.html
http://www.cliffordperformance.net/
http://www.inlinesix.com/
http://www.harlandsharp.com/inline_6.htm

http://www.34-chevy.com/

Afew more.
http://sohcsix.yuku.com/
http://jzedholden6.com.au/main/index2.asp
http://www.rbracing-rsr.com/compstaticcalc.html

http://www.classicinlines.com
http://www.xfalcon.com (six sub-forum)

Here's another one for the Ford Folks;
http://www.ford-trucks.com/forums/forum52/

One from the land of the Pontiac 261:

http://canadianponcho.activeboard.com/index.spark?aBID=118110&subForumID=425292&p=2

Here's a thread showing the different greens used by GM Canada:

http://canadianponcho.activeboard.com/index.spark?aBID=118110&p=3&topicID=26831642

and ;
http://www.fillingstation.com/
http://chevy.oldcarmanualproject.com/
http://www.canadianmilitarypattern.com/235%20&%20261%20Cubic%20Inch%20Modifications.htm
http://www.hotsixes.com/hotsixes/?page_id=4

http://www.webrodder.com