Bittech.net - Whats on Custompc usually appears there too.
Clunk.org.uk - Long term living reviews of motherboards.
techpowerup.com - lots of reviews and useful downloads

Obviously Hexus.net

and for the rest of the world beyond our shores:

Hardwarecanucks
anandtech
xbitlabs
madshrimps
guru3d
tweaktown

I have about seventy in my bookmarks but those are some of the main ones.