Rick Curtis
Excellent tutorials on E-Commerce especially for the powerclimb cart.

Magicbeat
Also know as the other J.S. or maybe that's me :~) and I highly recommend his server behaviors suite too. You just have to admire his work he's a server behavior creating machine. Anyway, after you see what's in the suite you'll wonder why this want not include in UltraDev to begin with. "I call this the must have add-on to UltraDev".

Charon
Master Jules site (Sometime I don't think he's human maybe he's a RDBMS in disguise)

DMXZone
George Petrov, Waldo Smeets (The Macromedia culture and more...)

Massimo Corner
Lots of cool things for all MM products.

Project Seven Development
I say DHTML they say Dreamweaver To A Higher Power.