All I know is that these websites have "how-to" instructions for knitting socks on circulars:
knitting 2 socks on 2 circulars (from socknitters.com):
knitting a sock magic loop style (from knitaddicted.com):
I hope someone else will come along and post if they have some special patterns though!
There is also a book which people rave about called "Socks Soar on Two Circular Needles: a Manual of Elegant Knitting Techniques and Patterns" by Cat Bordi which apparently shows how you can convert dpn sock patterns to Cat's knitting on 2 circs technique, and also has patterns. (If anyone out there has read this book, is it as good as all the reviews on Amazon.com?)