Spotted on Springwise

This is a great example of guerrilla marketing, known as the "This Ad Cost Nothing" campaign, the three-week initiative was designed primarily to raise awareness for the Salvation Army's Northern New England division. It was conceived and created in Portland, Maine, by local agency VIA Group, which turned to area businesses for help carrying it out. Part of the campaign included broadcast time and print ad space donated by traditional media; the majority, however, employed less conventional tactics. Pizza boxes and coffee sleeves were transformed into ad space for displaying the Salvation Army's logo and URL, for example, as were bathroom mirrors at local restaurants—with the help of a little grease paint. VIA employees and willing friends parked their intentionally dusty cars in downtown Portland, with the logo and slogans written on their back windshields, while dozens of shops sported the logo on their own windows as well. Painted rocks, tarps and tennis court floors were also among the more than 5,000 "creative units" included in the campaign.

Checkout the website and see some of the creative examples, some inspiration for the rest of us.