Cars (in this case a pickup truck) can get pretty disorganized on a long trip or when they are used as a mobile office. Over the years, I've tried a number of approaches to organizing the front seat from a commercial "car desk" to several attempts at a home brew solution.
The above is what I have been using for over a decade and it has served me well, both when I was commuting and on long cross country trips and even when renting cars far away from home. The case can be checked as luggage... pop the pads off the end and stuff it with non fragile stuff. With the above, the clips need to be taped down.
The starting point is an inexpensive wedge shaped tool kit which is designed to fit behind the seats of any standard truck. The following two pictures show an identical (very old) box which has been used as intended as a truck tool kit.
Very few mods are needed. The most important one is to attach padding material on both edges which will eventually secure the desk in the passenger seat. I used stiff pipe insulation foam tubes which are held in place using two plastic "upholstery buttons" which are pressed into holes drilled into the side of the case... the holes are small enough to hold the rivets, but large enough to allow the foam to be removed and stored inside the case.
I cut some holes to facilitate passing wires around inside the box and to allow keeping a 12v cigarette lighter splitter out of the way when traveling. There is a hole on the left front bottom which is large enough to pass a cigarette lighter plug to tap the car's power and it also serves to route the laptop power supply and usb cables when needed. You can see a three outlet adapter and the sony 12v power supply plus a 12v-5vdc converter which is wired directly into the adapter to power things such as usb hubs.
A few "envelope clips" keep paper from flying, A piece of self stick door bumper strip serves as a pencil keeper, and four pieces of soft velcro match the four patches of hook velcro on the back of the Sony Picturebook.
This package then fits nicely on the passenger seat with the cord exiting the corner of the case close to the car's cigarette lighter
The final simple step is to slide the passenger seat forward to clamp the cushions on each end firmly between the seat back and the glove compartment. This works in most cars, but on one where the cover had a large angle, it was necessary to slip a piece of cardboard in the glove box gap to provide something to push against. Before you slide the seat forward, take out anything in the glove box which you may need enroute and put it in the case.
I have intended to add a "map light" to the lid of the case, but the Ranger has one in exactly the right place so it hasn't been a priority, but has been missed in most of the other cars I have used the desk with.
As Marvin pointed out, while the tiny Vaio "PictureBook"
is a great traveling laptop due it's size, in the content of this page,
it could mislead size perceptions, so, in fairness, a snap using a more
"normal" sized laptop from the junk box is shown below.
I hope this helps anyone looking for an easy and inexpensive way to set up a "Car Desk"