I put this together today and thought I'd share. I've attempted to list every major skill or task that falls under the broad field of "game design." I then tried to create a kind of progression, based on which skills are desired prerequisites before learning or performing others.
This is very much a work in progress (I haven't even added any icons yet), so your comments are welcome. Click on the image for a large version.
Since this is mostly a graphical version of notes to myself, some explanations might be required. I'm not sure how much is obvious to the casual observer, however, so rather than write a lengthy essay explaining every last detail, I'll simply answer any questions you have in the comments here. Enjoy!