GREAT idea...posting this thread every Monday! We need to remind people to GET INVOLVED right away...this will be a close race, we need every volunteer we can get!!
Regarding magnetic plastic backing for stickers...I go to a copy/print center like Kinkos or other and you can buy magnetic backing in a 2 foot roll...they sell it by the foot.
Then I cut a piece (cuts easily with scissors)to fit my sticker, put the sticker on it and have a magnetic sticker...Advantages, I can move it from car to car, I can remove it, and I can post it higher than my bumper, where it can be better seen.
Last time, I bought a 2 foot by 2 foot magnetic backing for about $8, so the cost is really cheap to make mag stickers yourself!!