Real Desktop

 Thanks to the powerful physics-engine of Real Desktop, your icons behave now. They'll act like real objects that you can touch and move as if on a real desk. Keep in mind that this is a free version.

http://www.real-desktop.de/English/index.htm

Bitmap Combine

By using the program Bitmap Combine, you can overlay two picture files. They do not need to be the same size or even of the same type. A very unique tool that every creative photographer (and what photographer isn't creative?) should check out immediately.

http://www.tonytooth.co.uk/page11.html