With the new version of Photoshop, you also get a new cropping tool called Perspective Crop Tool which will change the perspective on a image. Check it out, it really is a cool tool.
In Photoshop CS6, the new version of Photoshop, you can use special cropping tool and you are done, but that doesn't mean you cannot achieve the same result with older versions.
Pretty simple and useful tutorial, where you will open a random photograph with smoke and convert it into something really not friendly for our environment.
