Save image to photo library on simulator

The path in which all the photos saved is:

/Users/USERNAME/Library/Application Support/iPhone Simulator/4.1/Media

4.1 or which sdk you are using

So the easiest way is to drag and drop a image on the simulator. The Simulator will open a webpage to your local file ("file://…") and then you can save it but holding your mouse key for 3 seconds or so. Then click "save image" and it should appear in your Photo Library.