This 3-hour Windows Media lecture by character designer Chen Yi-Chang (MULAN, TARZAN, ATLANTIS) contains a lot of solid insights. Also, here's a couple articles worth reading: a 1975 interview with Ken Harris conducted by Richard Williams (posted on the promising new blog SewardStreet.com) and this 1990 interview with Mark Kausler conducted by John Cawley for his book HOW TO CREATE ANIMATION.