Other
Csu: "Art, Philosophy, and the Philosophy of Art"
Excellent introductory article by Arthur Danto defining "aesthetics." Site has helpful links throughout and great discussion questions at end of article. Danto bibliography included.
ArtLex
Art Lex: Aesthetics
Definition of "aesthetics" according to ArtLex, a dictionary of art terms. Includes links to other important terms as well. A good place to start.