wxSmith is described as 'Code::Blocks plugin for RAD editing of wxWidgets applications'. There are more than 10 alternatives to wxSmith for Linux, Windows, Mac and Bloodshed Dev-C++. The best alternative is Glade, which is both free and Open Source. Other great apps like wxSmith are Zenity (Free, Open Source), Yad (Free, Open Source), wxFormBuilder (Free, Open Source) and wxGlade (Free, Open Source).
Anthemion DialogBlocks is a sizer-based resource editor that quickly gets you creating professional-looking dialogs, wizards and frames for deployment on Windows, Linux, Mac or any other supported wxWidgets platform.
Xdialog is designed to be a drop in replacement for the "dialog" or "cdialog" programs. It converts any terminal based program into a program with an X-windows interface. The dialogs are easier to see and use while adding even more functionalities (e.g.
wxMill is a drag-and-drop GUI builder for the wxWidgets framework. It can help you create wxWidgets based projects rapidly. You can edit windows in a WYSIWYG way, change various properties of widgets, and set event handlers.