If you’re curious about building your own computer or just curious about what all that stuff in your computer case is, then you’ll want to check out PCitYourself.
This site provides all kinds of information about the guts of a computer and how to select the components that will be best suited for the computer you want to build. For me, the highlight of this particular site is its great animation. There are a number of excellent 3-D animations that show how all the different parts of a computer fit together. Go give it a look.