This is what I'm using
http://cinemasupplies.stores.yahoo.net/succupmoun.html with an additional pan and tilt mount attached for better control.
For my purposes, this is an exceelnt mount as it goes to a piece of Plexi that's mounted to the passenger side dash (no passenger AB on my pickup). This allows full movement across the entire front window and the camera is easily adjusted on the pan/tilt head even while driving. If something is only shootable from a side window, simply reease the suction, peel it from the plexi and mount it to the side window! There's enough clearance that you still get full range of movement.
If your real brave and like to play with different camera angles, the mount is stable with a small camera to speeds of 85 mph. You can mount it just about anywhere you can find a smooth surface. I've done some real interesting shots mounted behind either front or rear wheels, on the hood looking back at the driver, on the roof looking back over the topper, etc. As a safety, I simply use a braided dog leash with little or no slack so if the suction does fail, it's very short fall without hitting the ground. I've yet to have the suction fail though.
I've taken the plexi and tied to the back fence at softball and baseball games to get views directly behind the catcher and umpire and even used it once for an overhead of the home plate. That worked till it got popped but a foul and knocked it loose from the fence. The suction did not fail.
Your really limited only by your imagination and smooth surfaces as to what you can do with it. We did a commercial for a motorcycle club out by Shidler where we had a 2 miles of viewable hilly roadway. We mounted the camera to the gas tank of the bike and had another camera filming the oncoming bike. A third camera was set in the roadway close to the gound to get the view of the motorcycle speeding away. Add a little bit of classic rock, the Voice Over narration and we had a really slick commercial. It's amazing the message you can convey in 30 seconds or less!
