the widest glass I have for the D90 is an 18mm sigma so 27mm @1.5x crop on the D90. It looks like shi* wide open @ f/2.8 though. The olympus 14-35mm wide open @ f/2 and sharp would be around the same focal length 28mm @ 2x crop. As far as I know there isn't any other lens as fast at that focal length.
Tokina 11-16mm man. It's ridiculous.