A little more detailed than you'll need, but still useful. http://www.gwc.maricopa.edu/class/bio202/cyberheart/hartint0.htm
Good for seeing the path of blood through the heart. http://www.texasheartinstitute.org/hic/anatomy/anatomy2.cfm
Good pictures of actual sheep heart specimens. http://www.hometrainingtools.com/articles/heart-dissection-project.html
Jackpot! Real pictures with links to different views. http://www.gwc.maricopa.edu/class/bio202/heart/anthrt.htm