I want to try to record the method I used for my sock while it's still in my mind. Even though knitting on one (or 2) circular needles is much simpler than on 3 or 4 dpns, it does require some special adaptations when you're using a pattern, because the patterns explain the decreases in terms of needle 1, 2, and 3, and you have to reinterpret that.
So first of all, you cast on all your stitches on one end of the long circular needle. Then you slide the stitches to the middle of the cord. Count half the stitches, and pinch and pull the cord through a space between the 2 middle stitches. Now you can slide the stitches back to the tips, half on either side.
Next, you need to make a nice smooth join. The method of exchanging stitches seems to work well for me. http://www.az.com/~andrade/knit/twocirculars.html
Move the first stitch on the left needle onto the right needle, and then slip the original first stitch on the right needle over and onto the left needle. Then the stitches on the farther needle, from whence the working yarn is coming, are pushed onto the cord, and you pull the needle so that you have just a small amount of loop on the left and plenty of free cord on the right side, and you knit. I pull the first stitch really tight each time to avoid ladders.
Ok, so the ribbing and the leg are perfectly simple. Round and round you go. When you come to the heel flap, it's perfectly simple since half your stitches are already on one needle and you just knit back and forth.
The tricky part is when you pick up stitches and then decrease. My method was to slide all the stitches back onto the cord and re-divide them so that each needle has half the stitches from the top of the foot, one set of picked-up side stitches and half the heel stitches. And then, place markers at the point between the top of foot and the beginning of the picked-up stitches on each side.
Then, when you come to the marker, look at where the sock is hanging down. If the sock is on the right, pass marker and then K2tog. And if the sock is on the left, ssk just before the marker. In the first few rounds, it's obvious where to do it because you are along side the heel flap, but as you keep going, you get further away and you need to pay attention.
When all the decreases are done and you're back to your original number of cast on stitches, slide the stitches onto the cable again and re-divide them so that you have the top of the foot on one needle and the bottom on the other. Knit round and round till you get to the toe decreases.
On each needle, K1 ssk knit across k2tog K1. Turn to the other needle and do the same:K1 ssk knit across k2tog K1. Continue until there are 8 stitches left on each needle and then kitchener them together. And that's it!
With one circ, it doesn't matter whether you have 64 stitches or only 16 or 8, it still works. I think this would work great on hats too--no awkward switching to dpns at the end.
If you know how to knit on 2 circs, just look at it for a moment, and you will see that if you slip one set of those stitches onto the free end of one needle, you can dispose of the hanging dangling thing and have a much neater little package of knitting. There's nothing to dangle because one end of the needle holds the working stitches, the cord holds the other half, and the other end of the needle is used to knit with.
Here's a picture of how it looks. Unfortunately, they don't sell the booklet directly. However, you can order it online here, $8 plus $4 shipping: http://www.jimmybeanswool.com/secure-html/onlinegen/currgen/FiberTrends/MagicLoop.asp
Don't waste your time or money on Cat Bordhi's book on 2 circs.
My needle is 29" Takumi bamboo, size 3 US, and it's plenty long enough for socks or mittens. The join is not as smooth as some, but then again the stitches don't fall off as easily either, so it's a tradeoff I'm willing to make.