When using these or any other ftp sites it is highly advisable to use an application like "Fetch" instead of using Netscape or any other web browser.
ftp://ftp.ime.usp.br/pub/music/
ftp://ftp.ircam.fr/pub/forumnet/max/
ftp://music.calarts.edu/pub/Max/
ftp://notam.uio.no/pub/mac/max
ftp://serial.music.uiowa.edu/pub/max/
ftp://wendy.ucsd.edu/pub/midi/max/
ftp://xcf.berkeley.edu/pub/misc/netjam/submissions/max
I would like to recommend "Sausage", it contains a large amount of music and sound related information, including a Max page. It was last updated in January but I plan to update it after I finish this.