My method in PSE/PS7: Use Magnetic Lasso Tool to select the area I do not want to blur. Then right click and Select Inverse. Apply Radial ZOOM Blur (In Blur Menu) and it is done. I am not well versed with PS/PSE and my method I believe is crude. I am sure you all will have a better method. The Idea was to have fun with it and I sure did. Thanks to my friend Cherie for showing me the Radial Blur.
Camera: Olympus C2100UZ, E-20N. The original photos are somewhere in my other galleries.

This shot is effectively a "double exposure". It is a 15 second exposure, followed immediately by a fast exposure to capture the moon - the two images then composited and enhanced in PhotoShop.