http://www.wyldesites.com
http://www.envisionnext.com
http://www.dickmansdesigns.com
http://www.fdsign.com
more or less in that order, maybe with the first two alternating in the first place
then you've some very efficient designers who throw very good work but I find their designs kinda cookie cutter like webinc and bluedesignstudios
and between those groups of great designers I'd put Quashe: not the most original, not the most efficient, but still more original than the second group's
there's a brazilian guy who makes some nice non adult stuff, but don't remember his URL and I've seen some nice work here and there but right now don't remember the designer.
Another one who wasn't mentioned in this thread is Madsights, there's a lot of people who loves their work. Personally, I can't see why, but if you're talking about designers he's somebody to keep in mind anyway