Icelandic or Russian Bind off

From BluWiki

This is a more elastic bind off than the Basic bind off. To do this you knit one stitch. Then you slip it back on to the right hand needle and put the left hand needle into it purlwise.

Now you knit the next stitch and pull the resulting loop through the first loop.

Keep this very loose and the resulting bind off will be pretty and stretchy.

The video for doing this is here