Beware that in the UK holders that are attached to the windscreen can cause your car to fail it's MOT test. Even worse, the police may decide that it constitues an unacceptable obstruction to your forward vision and choose to prosecute.
Also be careful that you don't position the mount/phone in front of any airbags. There are cases of airbags going off and launching phones / PDAs through the back window, or worse, into a passenger.
On a more positive note my P910 sits quite happily in a mount fastened to my fascia airvent. I find that having the phone lower down reduces the glare and makes the screen much more readable. The mount came from an orange shop and cost £9.99. As a bonus it has alternative fixing mechanisms, I use the one in my car air vent and another screwed to my Motorbike fairing. Very handy. | 
P900 in car mount 
Linear Mode
