This web documents every single item in the game, showing you where it comes from, how it can be made or what creature will drop it. It's a fascinating image and its possessed of a strange beauty. What you see above is just a small part of a much bigger picture.
It's also way too big to post here, in all its glory, so instead I'll have to link you to the full thing. You might notice that there's quite a few different strands for some of the materials, something that I guess is a compromise to prevent crowding or overcomplexity. Iron ore, for example, appears in several different places and originates quite a few chains of construction.
Of course, this is accurate for the latest version of Minecraft, but we all know version 1.5 is on its way and there may be more updates to come. It would be well worth keeping an eye on the Production Web's tumblr to see when it's updated.