I recently replaced the cabin filter in the wife's 2010 Q5 and the directions I found on this site were not entirely correct, at least for her car, so I thought I would update the procedure, which is stupid easy. This is part of the 15k service, which also includes an oil & filter change.
1. remove the passenger front floor mat
2. unscrew the two black screws holding the cover in place, just at the top of the carpeting. You do not need a screwdriver for this just turn the black *****.
3. remove the white plastic lid securing the filter by sliding it horizontally, away from the center console. Once it has moved an inch or so it will come off.
4. pull the old filter out and down, will need to bend it a bit to get it out.
5. install is reverse of above.

All this should take 10 minutes the first time and 3 minutes the next time. It helps to have a nice bright light handy. A new replacement filter was $22. I think the dealer charges over $60 for this service, which is really a rip. If anyone has trouble doing this and needs me to post some pixtures, just let me know and I will oblige.

 

Please note - there are THREE (not two) hand twist off screws that hold the foam cover that allows access to the cabin filter holder. The third screw is closest to the firewall and towards the center console.

 

Here you go... http://forums.audiworld.com/showthre...t=cabin+filter