I made this car trash bag for my dad for Christmas. He doesn't like when I buy him presents but he's okay if I make something for him. He's fanatical about keeping his vehicle clean so I think he will appreciate it. It has an adjustable stap to fit over a headrest or a little tab that can fit over a knob on the dash. It is a double bag -- there is an inner piece that you tuck a used bread bag into so you don't actually see the trash bag. I used heavy duty interfacing so that it would be fairly stiff and added buttons inside so that if you cut slits in the bag, you can slip it over the buttons to hold it in place. The idea is stolen, this time from Allyson Hill. I haven't actually seen one of her bags in person but I'm sure they are much better than mine :).
The outer fabric is echino nico bus in yellow; I kept the selvedge on the bottom and I really like how it turned out.