- a childrens tent  (7.50€)
- a plastic tarp, 185x160cm (1.95€)
- duct tape
- (old) bike inner tube, or similar rubber
All this fancy photographic equipment set me back less than 10€, since I already had duct tape and an old inner tube.
This DIY is almost missing the D part - you basically just put the
1) Make four (4) rubber thingies (this is the D):
- cut 1.5cm wide, 15cm long strips of rubber
- fold about 1.5cm of one end and wrap the folded part with tape, so you get a pocket (with the opening towards the rest of the strip)
2) Fold the tarp in half, so that is is 185x80cm.
3) Take the rubber thingies, and tie the end that is not folded to the tarp, one in each corner.
4) Take the poles from the tent and stick them in the pockets of the rubber thingies, crossing the poles at the middle of the tarp. 
The Lightrpanel is very light and can easily be handheld, so it can for instance be used it as a reflector or a scrim. 
If you unfold the tarp, you can double the size of the scrim/reflector, but it's not as rigid, and hard to use as a lightpanel.
One could quite easily make a big softbox by attaching a silver material to the sides.
The dimensions of the panel do not have to be as suggested here - you could make more of a striplight for instance.
After trying this out with the tarp, I decided that the concept was good enough to break out the sewing machine. The fabric is a little lighter, and takes up less space, than the tarp. The fabric version can be seen from image 7 onward.
Initially I connected the panel to the lightstand using a rubber wire (images 3,4,6), which is vert handy, but using a telescopic rod I could increase the distance between the flash and the panel somewhat, producing a more even lightdistribution.// Marc