You won't find art like this in a museum. Street artist or Installation artist use an urban environment and it's structures, accessories, roads, buildings, signs etc to creatively decorate and spread a message. Almost always, installation art has a powerful meaning, usually social observations. Sometimes it's just to be funny or just plain creative. These have been hand picked as some of my favorites and the internet is full of more, just a quick search away.
Great use of a storm drain, extremely well done. The juxtaposition of smoking and urban air pollution.

This artist uses tools to create gorgeous art in the dust on the windshields of dirty cars. Using a dirty car as a canvas is the type of art that can change the world.

Reverse Graffiti. This artist etches skulls out of the smog that is left in tunnels. This one was done in Brazil. Wonderfully representing the amount of pollution we create in our natural world.

Politically Charged. Rock Solid. Anti War.

Clever way to dress up a parking meter. The money made from these is candy to a cities economy.

This is hilarious, possible commentary on mass communication. Symbolizes the rate in which our world is growing ever smaller through mass communication.

Personal favorite. Such a great stencil and design. If we had more artist in the world doing these things...

The Irony behind this is great. Some installation art is just art for arts sake, without meaning or commentary. Twisted and weird.

Environmentally attuned street art. You may not of seen this in your town, but if you were to visit the Antarctic this scene would be abundant.

Extremely well done drain pipe with pixels. Amazing how much time an artist will put into a piece they can never claim to be their own. Sort of a Super Nintendo looking throwback reference.

Hopefully you enjoy these tidbits of street art and don't see them as vandalism, but a powerful way to spread a message. Art is the vehicle for change and change is a must in times like these.