In the wiki there is a short F.A.Q. for beginners in Lua.
Clicky
Lua beginner's F.A.Q.
Moderator: Moderators
i add a 'complete' (2-3 funcs missing) Lua OpenGl Api documentation for all those who aren't beginners anymore 
Lua OpenGL Api

Lua OpenGL Api
http://spring.clan-sy.com/wiki/Units:LuaCOB - somewhat outdated and incomplete, but still of some help
Add a new wiki for the SyncedCtrl interface. It nearly answers 90% of all questions (like: "is it possible with lua todo xyz?" etc.).
It is used by gadgets and only the GiveOrder commands work in unsynced code, too.
http://spring.clan-sy.com/wiki/Lua_SyncedCtrl
It is used by gadgets and only the GiveOrder commands work in unsynced code, too.
http://spring.clan-sy.com/wiki/Lua_SyncedCtrl