If you have a Mac that will still run old OS 9, and would like to try some challenging and fun genetics activities, you absolutely have to check out the Genscope project! This is an amazing (free!) genetics study tool that you will find both entertaining and educational.
I suggest starting with the "Dragon" species file - one of the features of the program lets you "give birth" to a dragon, then view the alleles on its chromosomes. By doing so, you can investigate dominance, recessives, co-dominance, sex-linkage, lethal alleles, polygenic traits, and more! For instance, one of the chromosome pairs pictured below for the dragon indicates that having no wings is governed by a dominant allele... switch both alleles to recessive and wings pop up on the dragon!
If you wish to tackle a more advanced topic, you can study pedigrees very easily by creating individuals and then mating them. A new generation of individuals pops up, which in turn can be mated with new individuals (or themselves):
Examining what individuals look like is as easy as clicking on them! You can also choose to view the individuals with symbols representing particular traits. Amazing!
Genscope also includes a well developed population study tool to examine the trends in a large gene pool, and the program even includes animations of meiosis and fertilization to illustrate gamete formation and how chromosomes "do their dance" when egg meets sperm. Here's a QuickTime movie of one such meiosis event:
