I recently viewed YouTube videos on a solar sinter and solar cutter. This is one of the most aha! inspiring technologies I've ever seen! Imagine what upscaling and refining of this tech could do: sinter your own house in the desert!

I can imagine an industrial fabricator with a gravity-fed tube delivering metered amounts of sand from an elevated hopper to a tool tip where the sun beam is being focused.

Must watch videos!
http://www.youtube.com/user/MarkusKayse ... end=7&ob=5

..and, how about building a mini SolarBot fabricator? I haven't looked around the 'net yet to see if anyone's done this.