I needed to make 15 simple cute bags for Girl's Camp in a few weeks (for 12-18 yr. old girls). So I used a little bag from Anthropologie as my pattern (even their baggies are cute!). You can make these any size you want, and they are about as fast and easy as it comes.
(Since mine are basically going to be disposable, I didn't bother ironing).
I started with a scrap of fabric that was 8x10 inches.