Knitting Tutorial – "Corrugated Knitting Tutorial – less elastic than regular knitting, but Oh, What Visual Dynamite! There are many ways to vary this. plus, it's perfect for knitting in the round." comment via KnittingGuru
splityarn calls this the "Easiest Knitted Sweater Zipper Install Ever" and it looks like it might be. I haven't tried it yet but I'll let you know if I do - my one attempt to put a zipper into a knitted sweater came out OK, but not this nice.