My "Powered by Ubuntu" stickers arrived today!
A few weeks back, I sent off for them from the System76 website. You can download them from the Free Software Stickers book and print them yourself, but of course you need the right self-adhesive paper and reasonable printer, so it's easier to get these guys to do it for you for free! They are ideal for replacing those Designed for Windows stickers most PCs/laptops come with. I have put the first sticker on my home-built desktop machine.