I've recently started a blog that some Greenfoot users may be interested in. It's targeted at those who know a bit of programming (i.e. I'm not going explain the very basics of coding), and want to understand the use of mathematics a bit better: either to see why it's useful, or to solve a particular problem in your games. It's called the sinepost, and there's a couple of posts up already on using trigonometry for doing angle calculations, with more posts to come in the next few weeks on things like wrapping around the world, and implementing movement systems. I'd be happy to hear feedback here, on in comments on the blogposts -- I hope it's useful to some of you.