Google Labs just released a pretty amazing product called the Google Body Browser. You’ll need a WebGL enabled browser to use it (Chrome, beta versions of Safari or Firefox) but you’ll likely find it worth the download. According to Google:
Body Browser is a detailed 3D model of the human body. You can peel back anatomical layers, zoom in, and navigate to parts that interest you. Click to identify anatomy, or search for muscles, organs, bones and more. You can also show share the exact scene you are viewing by copying and pasting the corresponding URL.
The address is http://bodybrowser.googlelabs.com