The two "make it" sites had great ideas and I basically combined the two sites and made myself the perfect bounce card. I bought two pieces of craft foam, one black and one white, and a package of velcro strips. White glue and a pair of sharp scissors is pretty well all you need after that.
With a simple twist vertical shooting is a breeze.
Attached with velcro, easy on easy off. Lays flat and takes up very little room in your bag.
I created a template and out of the two pieces of foam I made 6 bounce cards. I only have one external flash so I'm giving the extras away not including shipping. I figure $10 will cover the cost of shipping and the envelope. If you have a Paypal account send ten bucks to kansasA@gmail.com or simply email me if you don't and we'll make other arrangements. Don't forget to include your shipping address! I'll ship to Canada and the States but if you're willing to pay for extra postage I'll ship anywhere :)
If you'd like to see larger pics visit my Flickr site here.