How to design a CS curriculum for middle/high school?

I want to help my hometown high school develop a CS course, because I want to give something back and as a fun side project. The main challenge I see is delivering the message that CS can be fun, useful, and allow one to build incredible things. I took my first true CS class at Harvard's Summer School when I was in high school, and it was this really fun, mixed up collection of programming, history, cryptography, design, GUIs, algorithms, etc. It was weak in the department of giving me tools to do something myself, but that was probably it because it was the first in a series of courses. However, it equipped me with the interest to actually pursue the subject, and I also believe strongly, especially for CS, in learning how to learn and loving curiosity. I think showing the breadth of CS will both appeal to cynical teenagers and also engender a feeling of unity with the other subjects and teachers. Does anyone have any leads or ideas on some really good curriculum ideas?