I made it with a free pattern from Hook Me Up Crochet. Unfortunately the owner has taken the site down, but I was able to find it, sans pics, on the wayback machine. http://web.archive.org/web/20051124071511/http://www.hookmeupcrochet.com/Create/Patterns/Solomons_Knot_Shawl.htm
It was actually very simple, once I learned the stitch. It is the Solomon's Knot, also known as the Lover's Knot. I used the tutorial on about.com to learn how to do it. http://crochet.about.com/library/weekly/aa122698.htm
This shawl is made using some ribbon yarn from Walmart that I was able to get for $2 / skein. Oddly, I think everyone else made theirs with two skeins. I had to run back for a third skein to finish mine. I thought I was measuring my stitches, but for some reason mine came out bigger. Here's a hint for making uniform knot stitches. Put a mark on your crochet hook to mark the length you want your stitch to be. Then you can use your hook to measure each stitch and you don't have to pick up your ruler all the time.
Now all I have to do is get my shawl away from my 5-year old! (And for those of you who have already finished the next CAL, I'll be joining you if I can ever decide what color I want to use. lol) No wonder I'm always behind!