Corey Barker has a great tutorial in this Video Podcast from PhotoshopUserTV. http://kelbytv.com/photoshopusertv/2012/01/17/episode-291/
I was pretty impressed on what he was able to do with a simple picture of a yellow tree. I would love to see the zoomed up closeup of where he cloned it over.
Here is the episode summary:
Corey shows viewers how to use refine edge to do image retouching. Pete has a tutorial on using the path tool to create graphic elements like backgrounds. Dave shares some techniques to help make a repeating pattern appear seamless.