Take a look at my first picture. Don't be afraid to look. Just look at that ugly gap that would want to make your lovely hand knits socks look retarded and make the non-knitters in your life prefer store bought socks. When binding off toe-up socks, (I used Jenny's surprisingly stretchy bind off), all you have is the working yarn . You might find yourself in a dilemma. I know that you want to prove to all of your non-knitting friends that hand knit socks are something to drool over and not cringe at. I'm here for you and here is my solution. It is a common crochet technique.
Next, after threading yarn into your tapestry needle, you will insert the needle under both loops of the second bound-off stitch to the left . Note the helpful numbers that have been inserted into the picture--thanks Picasa. Draw the yarn through from front to back.
This is how it looks before tightening--kind of like the number 8 if you were looking down at it.