My So Called Scarf & Shifting Sands are both lovely.
My favorite though is the One Row Scarf a la Yarn Harlot.
Start: Cast on 26 stitches (to make it wider or narrower add or remove stitches in groups of 4 )
Row 1: *knit 2, knit into the back of the next stitch, purl 1. Repeat from * till there are 2 stitches left. Knit 2.
Repeat that one row every row until you can stand it no longer, your scarf is long enough or you run out of yarn, whatever comes first.