[wxLua] (5.1) - [wxWidgets] bindings for Lua 5.1. wxLua project provides its own IDE with a GUI debugger, a binding generator and a "wx" module for wxWidgets. The IDE is written in wxLua. wxWidgets provides native look-and-feel on Windows, Unix and Macintosh platforms wrapping the underlying toolkit (respectively win32 API, GTK+ 2.0 or Motif or X11, and Carbon API). Well-maintained.
[IUP] (5.0, 5.1) - GUI toolkit for Windows, GTK and Motif with Lua 5 bindings. IUP uses native controls in Windows, just like wxWidgets. The Lua binding has a very close Lua like API.
[VCLua] (5.1) - Lua Visual Controls, small native toolkit library for Windows and Linux/GTK2.
[Crank Storyboard Suite] (5.1) - Create and deploy user interfaces to a wide variety of operating systems (QNX, WinCE, Windows, Linux, Mac, ...) and rendering technologies (gdi, sdl, opengl, openvg, agtdk, direcfb, fbdev, ...) using standard graphic elements and Lua scripting to manage the glue logic. Also provides direct from Photoshop screen import capabilities and an integrated simulator and Lua debugger.
JUCE: [luce] (5.1/5.2) - lightweight, embeddable GUI toolkit based on JUCE.
[tekUI] (5.1, 5.2, 5.3, LuaJIT) - lightweight, modular, extensible graphical user interface toolkit; not a binding, but written in Lua itself. Available for X11, DirectFB, Windows, Linux framebuffer, raw memory. Customizable using cascading style sheets. Option for an inbuilt VNC server.
LibrariesAndBindings - lists other graphics libraries for OpenGL/3D, direct media access, images, plots/graphs, etc.