This article from A List Apart is a great reminder that even in 2011, the pencil is still one of the most powerful weapons in our arsenal.
Not being a designer-type by nature or by training, this idea of visual thinking doesn't come as naturally to me as it does to some of my colleagues who are always armed with a sketchbook, but I have observed its efficacy many times.
Sketching is unrivaled as a rapid prototyping tool, but more than that, it is a catalyst. In the world of design, as with any creative endeavour, the biggest hurdle is often getting momentum behind an idea. Sketching gives us something to like, to hate, or to learn from. It challenges linear thinking, and it invites other people into your ideas.
That's it. Just a little homage to putting pencil to paper and a reminder that sometimes sketchiness is a good thing.