:D
File folders are great for Temp leather pattern, Those heavy plastic folders work ok too. Luan (that really really thin wood) is ok for one that's more sturdy and you can sand it to improve curves and whatnot. I've made some from aluminum flashing I have sitting around but cutting with tin snips can be unwieldy and the edges can be sharp.
For transferring designs, I like those heavy sheet protectors, which can be traced over and over and are clear so you can have precise placement.
I'm about to go buy a few newspaper roll ends for sewing patterns for fabric and to use to cover my table for when I dye.