http://www.who.int/en/
I use this website all the time when we introduce new countries to the students. I think its hard to talk about diversity if we don't have an understanding of how other countries live. We often overlook health and standard of living when we teach, but this website and the statistics that it offers make that hard to do.

http://www.youtube.com/watch?v=hTlrSYbCbHE
As kind of a follow up to the previous site I posted, I've used this video as an activator in several classes. It lays out some of the key points of the Declaration of Human Rights. The kids seem to really like the video and it sparks a lot of good conversation on the topic of diversity and human rights.

http://www.un.org/en/documents/udhr/index.shtml
This document put forth by the United Nations sets a foundation for humans as equals. It would be most appropriate for use in an uppper level class. There's some other really good information that can be found on the United Nations' website.