I've been working on improving my "toe-up" techniques, and highly recommend Wendy D. Johnson's book, Socks from the Toe Up. The book provides several different methods of cast on and toe techniques, several options for heel treatments, and good suggestions for stretchy bind offs. The patterns progress from basic to more advanced cables and textures. The text is straightforward and explains why steps are necessary, which really helps when you want to change things up a bit. The photographs and drawings are clear and supplement the text nicely.
The second is Jeny's Surprisingly Stretchy Bind Off presented in Knitty Fall 2009. I had been using tubular bind-offs which are pretty, but time consuming and still not quite stretchy enough. The JSSBO is by far the stretchiest bind off I've tried, and is still attractive.
Still have lots of the Opal left - enough for some kids socks I think.