After 7 months of dealing with this annoying rattle, I finally beat it. I took the radio, climate control and both glove boxes out and had my wife drive around the block while I looked for it. It appeared to be coming from passengers side right behind the lower glovebox. Once we got home (was getting car sick from laying upside down under the dash) I stuck a light up there and felt around for a few minutes before I was able to get it to make the noise again. I dont know if its the same rattle that TerryB47 had but I found mine where two airvents connected just under the dash behind the lower glove box. There is a small piece of plastic that sticks out and if I grabbed it and moved it, it would make the sound loud and clear.
The piece is most visible if you come in from the radio, but you dont have to remove the radio to get it.
This is a close up of the culprit.
I found that if pressure were put on the vents the noise stopped. I had a bunch of felt laying around so I stuffed it tight between the vent and dash to push the pieces snug together.
Then I grabbed that small piece of plastic sticking out and shook the heck out of it. No more noise!!! Drove it around the block and down the road a few miles and its perfect!!
To fix this you dont have to take out the radio, but it does make it easier to see what you need to grab.
Hope the photos help someone out.
Mark