Took the 2008 Prius in for a free 1000-mile service and asked the Service Dept. to look into a noise/rattle coming from the dash area. After a lengthy investigation, they found that the noise was coming from insufficient insulation of the instrument cluster (center). Am happy to report that the problem has been corrected, but surprised that adequate steps are not taken in production to ensure that this didn't happen in the first place. This repair cost the Toyota organization 1.8 units/hours ($171) plus the cost of a rental car for one day, which pays for a lot of insulation! As an aside, when I picked up the car I found that it was VERY sluggish! After seeing that there was only two bars of charge on the traction battery, I decided not to panic and found that performance improved noticeably within the next ten miles as the traction battery charged. Did not realize just how much the performance was affected by the traction battery charge level.....
I also have the same rattle coming from the dash area. I was planning on taking my Prius to the dealership to fix the problem. Glad to hear it was corrected.
The other quick fix they use for creaks, squeaks, rattles anf ticks is to spray silicone all aound the visible mating plastic parts. This usually cures the problem if it's not hidden.