At Hinton Ampner, the National Trust property where I work, there is a small statue of a black servant holding up a small bookcase. It's a caricature of course, but it speaks volumes about racial attitudes in the 1930's. (Typically, this subject is not touched upon in the house, and is a silent reminder of these attitudes.) During research for my dissertation, I came across some racist cartoons, broadcast in the US and the UK - some of them were even shown as late as the 1970's! The site below shows a few clips from these shows. It's uncomfortable viewing, but necessary.
This site is also very interesting - it explains the history of 'blackface', racial stereotypes that were used to mock African Americans. For my undergraduate dissertation, I wrote about the 'mammy' character, which was developed during slavery and is still used today in pancake boxes (I took this photo three months ago in D.C.). Apparently, this image has been 'updated' to show a hard working mother, but it's still pretty shocking. The site gives a really interesting account of the stereotypes and their use in films and television programmes.