Here's what I did with the Buttons yarn using the Simple Baby Socks pattern in The Magic Loop booklet. I highly recommend this booklet if you'd like to learn how to knit socks with one circular from the cuff down and from the toe up.
These socks are knit from the toe, using a figure 8 cast on which can be a challenge to manage but produces the best sock toe. Last week I tried starting these socks while riding the bus but gave up after several attempts. It's definitely a task that needs to be done in a comfortable environment.
Keep in mind that this cast on is not only great for socks, but can also be used for other circular items such as hats.
Here's how the cast on is started on two circular needles. The yarn is wound around two needle tips in a figure 8 fashion.
[Note: 4/9/2006 - I just noticed that this picture is wrong. The yarn end should start be under the lower needle (left side of photo) and then wrapped up over the upper needle. When I get a chance, I'll change the photo. Athough, I think it's still possible to wrap the needles this way. Just be sure not to twist stitches as you knit them.]