There are many that come to mind, but in recent years the most commonly cited racist ones are the crows from Dumbo, the native Americans from Peter Pan, and the Siamese cats from Lady and the Tramp.
Were they seen as racist at the time or is that the product of hindsight and over half a century of progress since they were released?
I don't wish to discourage other commentators from providing answers, but this thread asking more or less the same questions has some great responses to contemporary opinions. To summarize, in the case of The Song Of The South, the 1946 film Disney has "buried" since the 90s, yes the movie was seen by many African-Americans as very racist when it first came out.