Wikipedia is a good model, and Contents is generic. Let's start with that but come back to this after we work through the lower levels. With all due respect "Roots" is just too geeky for most WE folks. :o)
I completely agree that "Contents" is probably the best title to use for WE.
Agreed, contents seems like the best choice for WE. In addition to WP, a number of other wikis use Category:Contents as the top-level, although I think Category:Categories is maybe more prevalent.
"categories" might be more prevalent, but I have been doing a lot of thinking about what our target audience needs to succeed without having to entirely re-educate them. For instance, rather than calling it the "Main Page" it could be called "home", and "Support" instead of "help" "practice editing" or "contact us". I think that calling it "contents" will tell them exactly what they should understand from it.