Bluewave
Forum Enthusiast
These are called Amazing Circles, and are produced using this simple technique:
http://brilliantdays.com/archives/2005/10/how_to_create_a.php
They are quite addictive, finding photos from your collection that work well, and then manipulating further if you choose to. A great group to share these circle creations, or just view a large variety is here: http://www.flickr.com/groups/amazingcircles/ (if you're a member of Yahoo email you can log into Flickr).
I've produced a Photoshop action (I know it works with CS/CS2) to make it even easier to experiment:
http://web.onetel.com/~tgriches/photoshop/AmazingCircles.atn