Going along with my plaid week …
Online Tartan Pattern Generator: I haven’t had time to play with anything but the default colors, but it’s fun! You could design a signature tartan for your own family or club or other affiliation and get it printed by Spoonflower.
The House of Tartans has another online Tartan design tool, only with this one you can actually order custom woven fabric and products with your designs.
I have a post brewing on the difference between Tartan and plaids — look for that later this week.