Lua developed a "culture of libraries" recently, and is catching up. Another part of the problem was that it didn't really have a proper module system until a couple years ago (partially due to the focus on embedding).

Besides LuaRocks, there's a collection on the Lua wiki (http://lua-users.org/wiki/LibrariesAndBindings), and the mailing list (http://www.lua.org/lua-l.html) is very active.

And yeah - if you know Javascript, you won't have trouble learning Lua. It's like Javascript with less gotchas and better performance.