This is a little toy I put together that I thought might be of interest: http://ibises.org.uk/Minkowski.html It's an interactive Minkowski diagram. You can add events and connect them up with straight-line paths, then Lorentz boost either to a specified velocity or to the rest frame of a time-like path. Below the diagram there are instructions (which I hope make sense) and some buttons that create some textbook diagrams. The page uses HTML5 features, so you'll need a fairly up-to-date browser - if you don't see axes and a grid, that's bad. Also, I gather that not all browsers implement the <input type="color"> tag. I think the page will work anyway, but you may require a resource such as this one to set the colours if you're not familiar with hex triplet notation. Any comments (physics or otherwise) welcome.