Two things I've noticed while reading these boards day in, day out: 1. Regular posters have traveled extensively not only in Europe, but around the world and are happy to share their knowledge.
2. There are many pre-travelers out there looking for advice similar to the "back door" philosophy for other parts of the world. Rick has already covered Morocco and Iran, and many people post here about Egypt. So....if Rick Steves were ever to add another option to the North, East, West, and "Boot".....let's call it the "European Periphery".... what places would you want to ask about the most? For myself, I think I'd ask about Egypt, the Caucasus/Black Sea republics, and depending on how far we push our periphery, India.
Definitely not the periphery, but Austrailia would be my main interest. And Hong Kong. If things ever settle down, the Holy Land and Africa and Russia would be next.