University of Arizona
University of Arizona: Dihybrid Problem Set
This site is provided by the University of Arizona and it gives great information on the subject. Good collection of dihybrid crosses which exemplify the issue of independent assortment. Work these once you think you've mastered th concept.
Other
North Dakota State Univ./mendel's Law of Ind. Asstort.
Good description of Mendel's findings and his second major principle.