I heard about the pinwheel blanket when I was looking for something more interesting than the usual rectangular baby blanket. I found the pattern by using Google. Through Judy Gibson's website I found Emily Ocker's cast-on for starting something in the center, and it worked beautifully!
I wanted to use up some yarn I'd bought before I knew any better, so this is made in stripes of most of the colors I had. Joan Schrouder's idea of garter stitch triangles leading to an all-garter outer stripe also worked very well. However, next time (and there will be a next time, there's lots of yarn left), I'll make it in all garter stitch and do the increases every fourth row instead of every other row. That should remove the odd flare at the outer edge. Since this was intended as a toddler drag-around-the-house and use up blankie, I don't care about the flare, and I don't think he will either.