I want to design/sell cute, fun website templetes - where do I start?

There are actually several different programs from Adobe that you can use to design a website with. If you are interested in designing only, you can look into Adobe Photoshop, Adobe Illustrator, and Adobe Fireworks. But I also suggest that you learn basic HTML and CSS (Cascading Style Sheet). This way you will know what the limitations are as far as designing goes. And as for leaning how to use the Adobe programs, it is fairly easy to learn.