Check this place out ... I'm just going to post the website since I don't know how to make the link work...
http://www.tolerance.org
It is really neat because you can take tests to determine if you do have hidden biases based on color, age, weight, sexual preference etc. I was surprised at some of my results, and it was an eye opener for me. I think we all have biases in some way or another against certain groups. Perhaps by recognizing where we are biased, we can start to make changes in ourselves and be more sensitive to others.
ETA - The link works (or did for me) and if you look on the website in the Dig Deeper section you'll see "find your hidden biases".