Hi Everyone- The Sock Fairy, here!!
The yarn I used was Moda Dea Sassy Stripes- it is a self striping yarn. I liked it because it wasn't too expensive, it was self-striping (which I think is just too cool), and it is a little heavier weight than most self striping sock yarns. It is 100% acrylic, but soft- good for growing little boy feet.
I put the socks on Ben's feet last night- he woke up in the middle of the night because he had a slight "accident"- when I went in to help him change his PJ's, you should have seen the smile on his face when he realized that he had his new socks on! Even at 4:30am, it was worth seeing!