wxformbuilder

wxFormBuilder is a RAD tool for wxWidgets GUI design.

Features:

Visual design of wxWidgets dialogs, frames, panels, toolbars and menubars
Source code generation for C++, Python, PHP, Lua and XRC
Support for AUI-managed frames
Support for wxWidgets 3.0 widgets
Available from Ubuntu PPA (ppa:wxformbuilder/release, ppa:wxformbuilder/wxwidgets)
Available from wxPack (https://github.com/rjpcomputing/wxpack/wiki)