(A good site on Gothic architecture, with a glossary and links.) Gothic Architecture.
(Visit many of the greatest Gothic cathedrals at this site.) Gothic Architecture.
(This site discusses the seven individual tapestries known as the "Unicorn Tapestries," some of the most beautiful and complex works of the Middle Ages.) Painting and Decorative Arts: Tapestry.
(This site has a brief but thorough discussion on Machaut, one of the most important Gothic composers.) Music.
(This site covers select sculptural works of the Gothic era found on and in French cathedrals.) Sculpture.
(A site devoted to Gothic works of art, from the cathedrals to illumination.) General information.
(This site is pretty comprehensive and you will find links to many other sites concerning Gothic art.) General information about art.