Pleased you've raised this subject,somegreatmovies.I only wish avant-garde films were more widely available.I particularly enjoyed the Quay brothers' weird short animation Street of Crocodiles(influenced by Svankmajer and Eastern European cinema).Their feature-length Institute Benjamenta has a luminous beauty.Anger's Inauguration of the Pleasure Dome is repetitive,garish and bombastic but visually exciting.Len Lye did some very interesting and original work in Britain in the 30's;Colour Box,Birth of the Robot etc.Similarly Norman McLaren in Canada.I suppose Bunuel(Un Chien Andalou etc)has become mainstream avant-garde.Maya Deren's Meshes of the Afternoon(quite eerie)was highly influential for post-war American experimental films.There's also Michael Snow:Wavelength etc.I've not seen Brakhage's Scenes from Under Childhood,which i know is admired by many.I enjoyed some Man Ray shorts-Etoile de Mer,and The Mysteries of the Castle of Dice-also Le Ballet Mecanique(Leger).Svankmajer's animations(Dimensions of Dialogue..)and live action combinations(Conspirators of Pleasure,Alice etc)are eccentric,well worth trying.Chelsea Girls(Warhol)and Scorpio Rising(Anger)are famous,but i wasn't over-impressed.I'm not very knowledgeable on the subject,have yet to see avant-garde classics Film about a Woman Who(Rainer),Zorn's Lemma(Frampton)and Tom Tom the Piper's Son(Jacobs).Would be extremely interested in opinions.Man with a Movie Camera (Vertov)might be described as avant-garde,though for many it's now become too much a mainstream part of cinema history to properly qualify,like early Bunuel,and Cocteau(Orphee etc) - anyway,it's tremendous.Definitions are difficult.   