Here are some great online animations on the menstrual cycle:
http://msnbcmedia.msn.com/i/msnbc/Components/Interactives/Health/WomensHealth/zFlashAssets/menstrual_cycle_dw2%5B1%5D.swf

http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html

http://health.howstuffworks.com/menstruation.htm