http://www.usoe.k12.ut.us/curr/science/sciber00/7th/genetics/sciber/punnett1.htm - step by step practice

http://www.borg.com/~lubehawk/psquprac.htm - easy monohybrid crosses

http://www.biolessons.com/lessonplans/genetics/punnettsquare/default.asp -easy step by step