Brother Voodoo and Luke Cage (when he was Hero for Hire) are good examples of stereotype black characters. DC comics actually has a character called Black Lightning, as well as John Stewart (3rd Green Lantern from Earth) and Static Shock. Also John Henry Irons and his niece Natasha, both of whom were called Steel at different times. Tyroc, from the Legion of Super Heroes, sported a huge afro in the 1970s (as did Black Lightning) when he was first introduced, though it's hard for me to say if this is a stereotype or just a reflection of the times (or even if there's a difference). Also in the LSH were Kid Quantum and XS, both good characters.
I don't know how much stereotyping/discrimination you will likely uncover. The worst stereotypes, of course, are seen in film, particularly in criminal roles. In his early years, the Falcon dealt with racial issues. Captain America issues 130-135, 143, 153-156 all bear looking at, if memory serves. The cover gallery I just referred to didn't hurt either. http://www.coverbrowser.com/covers/captain-america/5
The Sons of the Serpent were twisted patriotic xenophobes who hated foreigners and worked to spread their message of hate in the Avengers #s 32, 33, 73 and 74. If I remember right, racism was a big part of what they stood for. They also were in Defenders #s 22-25. I seem to remember something about them framing the Black Panther, but didn't get a close look at them until the Defenders story arc. This was back in the 1970s. Other stories featuring them can be found here: http://www.marvunapp.com/Appendix2/sonsoftheserpent.htm
I guess what you're looking for are more or less unintentional examples, stuff resulting from prejudice or ignorance on the part of the writers, but I thought you might find these examples useful, especially since they go back to the 1960s.
Your project sounds interesting. Good luck with that.