The web sites listed below have excellent postings of pictures of parasites.  In most cases they are almost too ideal and do not represent what you would find in a typical specimen submitted for analysis.  Nevertheless, they are useful adjuncts to helping you study this material. 

http://www.dpd.cdc.gov/dpdx/ 
Web site of the Centers for Disease Control and Prevention in Atlanta, Georgia

http://www.life.sci.qut.edu.au/LIFESCI/darben/paramast.htm
Large image list of medically important parasites.

http://www.biosci.ohio-state.edu/~parasite/home.html
Some of the images contained herein are labelled so you can identify internal structures.

http://www.cdfound.to.it/HTML/atlas.htm
Good atlas with other useful diagnostic information.

http://www.medicine.cmu.ac.th/dept/parasite/official/image.htm
Image listing from Thailand.