Lua:Main

Lua FAQ
Lua_Beginners_FAQ
Category:Lua (shows which interfaces are loaded by LuaUI,LuaRules,etc.)
Forum topic with some basic information about gadgets
Forum topic with a manual on Spring lua scripting

Interfaces (last update: 76b1)

System
Lua_System

Const
Lua_ConstGame (holds game relevant constants)
Lua_ConstEngine (version & buildflags)
Lua_ConstPlatform (Current OS, video driver etc)
Lua_ConstCOB (COB, Explode, EmitSfx)
Lua_CMDs (documents all CMDs and CMDTYPEs)

Defs
Lua_UnitDefs
Lua_WeaponDefs
Lua_FeatureDefs

GameState
Lua_SyncedCtrl
Lua_SyncedRead
Lua_SaveLoad (engine-assisted Lua save/load)

Client
Lua_UnsyncedCtrl
Lua_UnsyncedRead
Lua_Lobby

OpenGL
Lua_OpenGL_Api
Lua_GLSL_Api (OpenGL Shading Language)
Lua_FBO_and_RBO (Framebuffer and Renderbuffer Objects)
Lua_UnitRendering (manage unit LODs and materials)
Lua_ConstGL (some OpenGL constants)
Lua_Fonts

Unit Physics
Lua_MoveCtrl (changes the physics of single units)
Lua_PathFinder

Engine
Lua_VFS (used to access files in the virtual filesystem, e.g. modfiles)
Lua_Scream
Lua_BitOps
Lua_MathExtra
Lua_Socket

Other useful tables
LuaCallinReturn
WeaponDefNames
UnitDefNames

Official Lua documentation
'Programming in Lua' book online
Lua 5.1 Reference manual
Lua tutorials

old Wikis (outdated)
Lua_SyncedInterface
Units:LuaCOB
Lua_Startscripts