ok, I have a question.  I've searched this site & others, but it seems what I'm finding is not giving me specific enough info for my needs.

We're trying to design passive solar into our house.   I understand the concept, and I understand what I need to look for in windows but I'm struggling with the overhangs.

I know that the width of the overhangs is important, but I can't seem to find anything to tell me how wide they should be. 

I saw a reference to a site that has a calculator/animation that shows the effect of different factors, but unless I'm just dumb it still isn't telling me what I should be doing..

This is the site I looked at..

http://www.susdesign.com/overhang/

Actually, that site is perfect for your needs. I used it to design the overhangs for my house. While it will not "tell" you what you need as if you had paid an architect to design the overhangs for you, it can certainly be used. Once you have entered the relevant information (i.e. your location on the planet and in what direction the house faces), you can begin experimenting. If your window sizes are already known, your only variables will be the width of the overhang and the height of the overhang above the window. If your window sizes are not yet known, you can also experiment with those as well.

If you are in North America, and you are looking to get heat in winter and keep cool in the summer, you will usually want to make sure the windows are mostly or fully shaded on June 21 and mostly or fully exposed on December 21. Depending on the climate in your location, you can adjust for more or less sun exposure (more or less heat gain).

Alternatively, the owner of that site offers overhang design services for a few hundred bucks.

You can see my overhangs on www.GouinGreen.com.

Hope this helps.

Ed