I use a magnet mount 5DB antenna from:
http://www.fab-corp.com/
The GPS is a Garmin eTrex Vista that sits on the dashboard. Serial to USB converter to the Toshiba Laptop with 2 batteries and a DC-DC converter plugged into the Cig.Lighter.
Obviously a Lucent card & netstumbler and usually a dos prompt and languard net scanner running.
Nothing is mounted cuz there's usually allot of car swapping.
There are allot more elaborate setups. But this is simple enough.
What you lookin to do?