I might have been a bit rash but due to the fact that wikimedia.com was stolen by a cyber-squatter I went ahead and bought wikibook.com and wikibook.org for the Wikimedia Foundation (somebody else could go ahead and buy the plural if they want - but I may still beat them to it).
My thoughts are this; Wikibook could be a new uber-project aimed at creating a host of different types of e-books. Different broad types of wikibooks would get their own sub-domain.
So for example textbooks would be at http://textbook.wikibook.org while fiction would be at http://fiction.wikibook.org. Internationalization would not be accomplished by sub-domains but by having different directories for each language. All English language textbooks, for example, would be at http://textbook.wikibook.org/en/ and all Spanish language textbooks would be at http://textbook.wikibook.org/es/.
This of course is very long-term planning for where Wikimedia may go in the next several years but IMO it is an obvious extention of where we are already going.
I'm still open to better ideas on what to name the textbook project though (if people think that project should have a very specific name). My above purchase was impulsive but I would probably secure other domain names for Wikimedia if good names are proposed.
But I kinda like the idea of having one domain name for an uber e-book project if for no other reason than that would reduce the domain name registration fee load on the Foundation (which is US$100 for 10 years ; I'm a cheapo and only registered the domain names for a year at 20 bucks each, though).
--Daniel Mayer (aka mav)