Stanford University
Comparison of Free Jazz to 20th Century Classical Music
A very indepth examination of free jazz. Site contains music theory and specific illustrated examples.
Other
European Free Improvisation Pages
A site about the European free improvisation scene. Contains articles, mp3's bibliography and videos.
Other
Jazz Improvisation Primer/ Free Improvisation
A look at what makes free jazz musically unique. Contains specific examples of free rhythm and tonality.
Other
Oculus Magazine: Free Jazz
A short description of the free jazz movement, and a timeline of important movements in jazz.