Do you know QR codes? Pretty old stuff, uh?
A free service called Likify allows you to show your appreciation in the only way that counts: a thumbs-up on Facebook.
The service lets you generate a unique QR code, which can fit in posters, flyers, store fronts, advs, etc.
Each time someone scans the barcode, the number of Likes is tracked, supplying valuable statistics on where and when your items were liked.