Lgob is a gui-toolkit for Lua. It is a binding of Gtk+, Gdk and Pango and more... It is not officially released yet, but is quite stable and usable. It certainly is elegant, small and fast. What is great about Lgob is that it supports all versions of Gtk+, Gdk and Pango.
More info at http://oproj.tuxfamily.org/wiki/doku.php?id=lgob