I found two sites that look at the inside of a Wii game machine from Nintendo. Popular Science has 16 photos while informit.com has a complete tear down with instructions. Both are very good, but informit.com gives you much more information including a nine minute video. In addition, CNN posted an AP article on how the motion controls for the Wii and PS3 work.
I also found a link to some handiwork where someone figured out how to get to the Wii Shop store.