The best all-around source we've found (which, despite its name, is not focused solely on women) is the WIMN's Field Guide to Media Research from Women in Media & News. They have links to articles and data on Media and Women/Gender, Media and Race, Media and Youth and Media and LGBT People.

Updated Feb. 2007 (most data from 2005): Media Report to Women, with statistics on Women’s Portrayal in News and Women’s Portrayal in Television Entertainment.

November 2005: The National Urban League released "Sunday Morning Apartheid: a Diversity Study of the Sunday Morning Talk Shows."

October 2004: Survey of African Americans About HIV/AIDS Media Campaigns: A national survey of African Americans reviews aspects of the Rap It Up and KNOW HIV/AIDS campaigns, which are ongoing HIV/AIDS public education partnerships conducted by the Kaiser Family Foundation with Black Entertainment Television (BET) and Viacom, Inc., respectively.

The National Association of Hispanic Journalists found in their 8th annual survey, released December 2003, that media offer scant and stereotypical coverage of Hispanics, America’s largest and fastest-growing minority.

The Media Awareness Network's Statistics on Minority Representation (1994-1998) has both U.S. and Canadian data on minority portrayals in media as well on hiring and employment of minorities in newsrooms.