The majority of the i7 mainboards I see have 6 DDR3 slots and most can support 24GB RAM which is nice.
Here are a few
Asus P6T Deluxe
http://farm4.static.flickr.com/3183/2784604434_2663e25bc0_b.jpg
Asrock X58 (Asus's budget brand)
http://www.xbitlabs.com/images/mainboards/asrock-x58-supercomputer/board_big.jpg
Gigabyte EX58-UD5
http://www.jatoncomputers.com.au/images/GA-EX58-UD5.jpg
MSI X58 Eclipse
http://pic.xfastest.com/MB/X58/X58-ALL-15.jpg
DFI Lanparty X58
http://www.images.clunk.org.uk/reviews/dfi-ut-x58-t3eh8/dfi-ut-x58-full-board-no-extra-cooling.jpg
BIOSTAR Tpower
http://resources.vr-zone.com/uploads/visionary/newspics/Oct08/07/TPOWER_X58_1.jpg
EVGA X58-SLI
http://www.techpowerup.com/img/08-11-17/132-bl-e758-a1_xl_8.jpg
Foxconn Rennisance
http://pic.xfastest.com/MB/X58/X58-ALL-16.jpg
XFX X58
http://img.hexus.net/v2/motherboards/intel/X58/XFX/MoboT-big.jpg
Here are a few
Asus P6T Deluxe
http://farm4.static.flickr.com/3183/2784604434_2663e25bc0_b.jpg
Asrock X58 (Asus's budget brand)
http://www.xbitlabs.com/images/mainboards/asrock-x58-supercomputer/board_big.jpg
Gigabyte EX58-UD5
http://www.jatoncomputers.com.au/images/GA-EX58-UD5.jpg
MSI X58 Eclipse
http://pic.xfastest.com/MB/X58/X58-ALL-15.jpg
DFI Lanparty X58
http://www.images.clunk.org.uk/reviews/dfi-ut-x58-t3eh8/dfi-ut-x58-full-board-no-extra-cooling.jpg
BIOSTAR Tpower
http://resources.vr-zone.com/uploads/visionary/newspics/Oct08/07/TPOWER_X58_1.jpg
EVGA X58-SLI
http://www.techpowerup.com/img/08-11-17/132-bl-e758-a1_xl_8.jpg
Foxconn Rennisance
http://pic.xfastest.com/MB/X58/X58-ALL-16.jpg
XFX X58
http://img.hexus.net/v2/motherboards/intel/X58/XFX/MoboT-big.jpg
I'm surprised they can pack in 6 RAM slots on those things.