Easy site builders for specific markets. Weebly is a good, general-purpose site builder. But there are a lot of markets that could use more specialized tools. What's the best way to make a web site if you're a real estate agent, or a restaurant, or a lawyer? There still don't seem to be canonical answers.
Obviously the way to build this is to write a flexible site builder, then write layers on top to produce different variants. Hint: The key to making a site builder for end-users is to make software that lets people with no design ability produce things that look good—or at least professional.