Check out Melissa Morgan-Oakes book, "2-at-a-time Socks". It's very well written and there are some great patterns in there. And you'd be doing two at a time on one long circ.
BUT, just for giggles, check out this one - two in one socks! It's a hoot! You work from two balls of yarn and are knitting one sock inside the other.
This is an even better one -
I saw these and got FASCINATED! Gotta try it, at least once.
And there's another video that shows how to cast on but that one slipped by me. I'll find it, though, since I really want to play with this as soon as I have the time!
Good luck and have fun!!!