I'm thinking of changing things up here at Speakeasy, and want to make use of grids for the next design (not that I haven't used them before, just that I want to try and give myself some limitations to work around). I recently read Subtractions presentation, "Grids are good" (PDF), and remembered that I had tripped across a grid background a little while ago.
Now, Subtraction's grid calculations require math - something I'm not very good at. So in order to play around with and test, I built The Grid-r-atr. Go and have fun with it!