Around the time I got my first computer, when I was still amazed by its capabilities, I came across "isometric" paper - paper with a triangular/hexagonal pattern of dots. I thought it was really cool to be able to draw 3D shapes so easily, and I wondered where I could get more of this paper. I hoped that the programmers had included an isometric grid with the sample images in Paint. Hey, everyone needs graph paper.
I found this website, http://incompetech.com/graphpaper/, that does just that. They have a wide range of graph paper, and even allow you to customise the spacing, size and colour of the dots!
I'm looking for graph paper now because I'm trying to do something like http://www.moillusions.com/2007/02/soulwax-cd-cover-illusion.html