I'm using Attic 24's ripple tutorial (you can find it on Ravelry). It's a treat, and this isn't the first - or the last - time I've used it.
Naturally, the yarn is a Rowan Pure Wool DK. What else? On a 4mm hook.
It's heading towards becoming a rather large baby blanket. I'll probably finish it next month once I've bought more of the light purple yarn. (I bought 4 at the end of January. No more till next payday!) The debate raging in my head: what kind of border?