Karmastitch on Ravelry just asked me how you knit two at a time socks and as she flattered me by complimenting me on my blog, I told her I'd write a tutorial!
There are obviously a couple of ways to knit a sock: toe up, cuff down, DPNs, Two circs, Magic Loop.
I'm going to try and show you toe up on Magic Loop and Two circs (the pics will be the same, but I'll add explanations), the method works exactly the same way if you work cuff down.
Now, obviously you need your needle of choice and some nice squishy yarn!
You can work in two ways, you can either split your yarn and work from two individual balls, or you can do what I do. Wind your yarn into a centre pull ball and work from either end - one from the centre and one from the outside!
Cast on sock #1 in the usual method:
Now, drop the yarn and pick up the yarn from the other end or from your second ball. Now cast on in exactly the same way:
As you can see the long circ (I use an 80cm for TAAT ML) doubles back on itself so that the points are together.
I know it looks a bit daunting, there seems to be cables, points and yarn everywhere. Identify and mentally dismiss the yarn tails which will be darned in later on. All you need to worry about are your needles and your two strands of working yarn - one for each sock.
Now, pull the excess cord out of the back stitches
Leave a little loop at the other end sticking out. Now hold the longer bit in your right hand and the needle with the stitches in your left hand. The yarn should be attached to that right hand back stitch.
Knit the first stitch on the needle and pull it quite tight (this will prevent laddering). Knit across sock #1. When you reach the gap between your socks
Drop the yarn and move the stitches down the right needle slightly (leave a little loop at the start). Move the stitches of sock #2 up to the end of the left needle.
Again you should be able to see the working yarn for that sock on that back stitch, pick it up and repeat the above instructions.
When you get to the end your needle points should be pointing left and the middle of the cable should be pointing right (which is the complete opposite of what you started out with).
Now flip the whole thing as if you're turning a page in a book so that the points are pointing right and the loop is pointing left and off you go!
Hey - you just knit a round of TAAT toe-up socks using Magic Loop! 
So, how do you work on two circs?
In exactly the same way, but instead of two points, there are four!
Divide your sock in half, the front of the sock (this is the top of the foot too) on one needle and the sole of the foot (this is the back of the leg too) on another needle. To knit, push your stitches onto the needle point, now pick up the other end of the same needle and knit across your socks in the same way I've detailed for ML.
When you get to the end, flip your work around and do exactly the same as above but using the other needle (because this is the needle that the other side is sitting on!)
It sounds so difficult if you just read it without trying, I know it does, because I did that loads of times - it looks complicated and fussy. But if you just do it as you read, (hopefully) you'll have that lightbulb moment too!
If you need help, leave a comment and I'll reply the same way!
