I think I have the Speedometer ring rattle disease too, thanks for the tips on how to fix it guys.
Speaking of super annoying rattles....My passenger door rattles quite loudly. If I put pressure on the door panel it stops. Sort of unsafe to drive with your hand on the other door so I wedged a piece of plastic dense foam between the seat and door panel. The rattle has stopped but it looks stupid. One of these days I'll take it to the dealer.

 

I solved the problem on mine. It was the throttle cable that was touching the bar that holds the hod open, I could even see a mark on the cable from rubbing against the bar. I have an '06 with 800 miles on it and the rattling at low speeds (approx. 1,000 miles was bothering me). I moved the cable, there is a thicker cable which is hold in place by a metallic hook, just move it out, place the throttle cable first and the thicker cable back, the hook will hold both in place. I've been using the car for 1 week and no more noise.

 

The round thing is about the width of a CD-is the horn that small?

DrG