Here's where I put my TomTom, a pretty obvious position to mount a small gps. It's perfect to see and operate, it's out of the worst sunlight and can not immediately be seen from outside. I have not had any problems acquiring satellite connections from this position either.
The OEM TomTom mounting leaves all the cables lying around. The holder I got from Carcomm (CNM-167) takes care of both the power, computer connection, audio, and TMS antenna for traffic messaging.
Getting the cables out of the way required a little bit of drilling but that's all.
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Then on the right-hand side of the dashboard I have an offroad navigation setup based on a scavenged Thinkpad X40. Below it is shown running Google Earth full-screen. The plate is aluminum bent to spec at a metal workshop.
On the right side I put in three USB ports for keyboard and memory sticks. There is a red on/off button that very quickly takes the PC in or out of sleep mode.
When I want to use the keyboard to set up the system I just plug in a small Thinkpad keyboard to one of the USB ports and off you go. The Thinkpad TrackPoint is brilliant to use even when driving on rough terrain where it is absolutely impossible to use a touchpad or mouse.
View from the driver's side. The wires are run behind the dash. This includes the powersupply that goes to the 2nd battery, the gps antenna that goes up into the front window frame, and the audio aux connection so I can play MP3s over the FJammer. On the door you can see I've stuck the keyboard pouch so its out of the way when it's not used.
(The above is just abbreviated from the "build thread" I posted
here)