How do you make these kits, could do with doing some?
First of all, you probably hadn't been replied to earlier as I think this thread is discontinued. And you'll need a tool. Either Smart Shirt Designer (this is the easiest way but it only has basic templates), or PhotoShop (more complex, but more rewarding!). I'll post links here.
Smart Shirt Designer
PhotoShop CS2 (this has been legally released as freeware)
Also, you'll need templates to create kits on PhotoShop.