stretchy cast off.

I'm posting this so that I can refer to it later... found at Weebleknits. (it was the 2nd result in my Google search)

Elizabeth Zimmermann's Sewn Cast off from Knitting Without Tears

Break yarn, leaving a tail about 4 times as long as the circumference of the sock. Thread a tapestry needle.

* sew forward (right to left) through two stitches as if to purl, leave the stitches on. Sew backward (left to right) through one stitch as if to knit and remove the stitch.
Repeat from * until you run out of stitches. Work in tail on the inside of the sock and trim any excess.

Denise's variation for circular knitting (from http://www.socknitters.com):
For the very first stitch only, after you go backwards through it, do not remove it, instead move it to be the last stitch on the final needle. It will then become the final stitch to be cast off. This gives a neater finish to the end of the round.

Via Weebleknits: Stretchy Bind Offs