I consider myself to be a usability dilettante; I suppose I'm an unlicensed practitioner of usability science. Some people find this stuff really boring, but I like to think BabyUniverse is better because of my informal study of it. A few usability sites of note: Mark Pilgrim's Dive Into Accessibility (new, blog-oriented), Boxes and Arrows, usabilitynews.com and of course Jakob Neilsen's useit.com -- but you already knew that last one, right?