Have you reviewed the top paragraph of the Rosetta@home project homepage? It tells you exactly what you are contributing to in very non-scientific terms that anyone can understand.

You will also be helping our efforts at designing new proteins to fight diseases such as HIV, Malaria, Cancer, and Alzheimer's...

Since these diseases are still not "cured" and there is no vaccine for them, the efforts you are helping is the progress towards those goals.

...and by the way, the teraflops numbers are for all of us combined. Not just for the user of the day posted next to them.

I'm a non-techy person and I run the program because I think it's all for a good cause but I can see nothing obvious and up-front on the main page which lists any of the results the project has produced to date and what it's currently working on. If I were you I'd put that out there right up front so people donating their computer's time to this project have some idea what they, as part of the project, have accomplished. From the main page I can only tell how many teraflops some super-users computer has cranked out and, with some digging, find the forums which don't give me a straight up answer. I'm not deep into the science, I'd just like to know what my computer has contributed to. I'm donating CPU time to this, since it seems slightly more relevant than cranking through space noise, not working on a protein folding thesis. You need to put some bait out there so the average user thinks they're participating in something more than just a generate-the-most-teraflops contest. I could do that with any project.