I didn't like the "store-bought" iPod holders, since they use the cupholders (and where are the cupholders on an E???? On the floor, where you can't see/reach the iPod!) This is my homemade "Stealth iPod Mini Holder". It's V1.1 - further modifications sure to come! It's 6061T6 aluminum, slides in and out of the vent ducts in a snap and when it's not there....it's not there! I used rubber tubing over the "fork" part so as not to scratch the plastic and for bounce resistance. Right now, it's a little too tight.
(My boss is a good 'ol boy about letting me make stuff like this - especially when I don't TELL HIM! :D )

http://groups.msn.com/BicyclingForumPicPost/virtualbikeride.msnw?action=ShowPhoto&PhotoID=6487

Excellent work! You better file a patent quick and while you're at it whip up a design for full size iPods too.

You could probably sell your dash mounting design to someone like http://www.proclipusa.com/frameset.htm although they have thier own holder designs for both the iPod and mini.