Ute Lennartz-Lembeck knit this rainbow sweater for a weeping willow in the German town of Velbert. It's called Yarn bombing, it's a type of street art that employs colourful displays of knitted or crocheted yarn rather than paint or chalk.
In the fall, a group encased trees throughout the Ped Mall with sleeves of yarn, like this. Think of wrapping the quilt you have in your basement around a tree and letting it shrink to size as it wets and dries. This is not unique to Iowa City; in fact, "yarn bombing," as it is called, is growing to be a widespread feminist form of graffiti art: http://www.nytimes.com/2011/05/19/fashion/creating-graffiti-with-yarn.html
Dallas, Texas- There is an anonymous knitter spreading warm and fuzzy love around Dallas, TX. Going only by the name of K Witta, this thoughtful knitter is looking to brighten someone’s day and perhaps be the reason for a few smiles. K Witta’s yarn bombs are created with only recycled yarn.