There is a book out there called "Socks Soar on 2 Circular Needles" It's a great book and for a beginner like me I was able to make a beautiful pair of socks.
I have a friend that attends a knit nite (too far away for me to go) where someone discovered how to knit 2 socks at the same time on just 2 needles. She says it also works well with sleeves because it ensures that everything is the same length.
All I know is that you need 2 balls of yarn. One for each sock. I tried it myself, but had problems from the start. After casting on and dividing the stitches, I had no way to reinforce the open end. Anyone use this technique? Anyone have any advice on how to start it? I am working on a sweater, and it would be nice to do both sleeves at the same time.