lua-mode.el with syntax highlighting, auto-indent, interactive Lua shell, paren and brace matching, auto-move to function or block begin/end can be found at . More recent version is available at 
Note the current lua-mode.el is a bit screwed up with regard to usual emacs conventions – in particular, it gives underscore (”_”) word syntax, which can be very disconcerting to an experienced Emacs user…
FlymakeLua – syntax checking for Lua.
LuaBlockMode – highlight matching block