University of Arizona
University of Arizona: Blood Types Tutorial
This site from the University of Arizona describes how blood type is passed on from parent to child. The tutorial covers the genetics of the ABO blood groups as well as Rh factor. There are even practice problems and blood type calculators!
CK-12 Foundation
Ck 12: Life Science: 3.14 Non Mendelian Inheritance
Learn about some examples of inheritance that do not follow Mendelian inheritance rules.