The help page for this site appears to be in Japanese, but this is a great site for creating background images for tiling on the <body> element of a site (or anything else if you wish) - pick a colour, move the sliders, tick the box....it's fairly easy to work out how it works and to create the right tiled image for your site. Once you click 'make', you get the image, a sample of what the image looks like tiled, a sample of text over the background image, and how it looks with another colour overlaid. Nice little tool and a lot less tedious than drawing pixel by pixel in your graphics app.
http://lab.rails2u.com/bgmaker/<edit>
And another very nice one where you can draw with pixels and see the tiled effect as you're drawing -
http://bgmaker.ventdaval.com/</edit>
