This is the coolest find in a long time, I am so exited. The Box Maker website has all different box templates. You plug in the dimensions you want and print out the cutting guide. It couldn't be any simpler. [box maker]
From the site:
Need to wrap an odd-shaped gift? Create a box for it! Measure it up, choose a template and print it. This page is a resource for DIY artists, graphics designers and everyone who likes paper crafts. It contains an ever growing number of templates for gift boxes and increasingly more other interesting things that can be made out of paper. What makes this site special is that the templates are all dynamic. You can customize almost all dimensions. Have fun!