Zenity!

CocoaDialog is an OS X application that allows the use of common GUI controls such as file selectors, text input, progress bars, yes/no confirmations and more with a command-line application. It requires no knowledge of Cocoa, and is ideal for use in shell and Perl scripts (or Ruby, or Python, or... etc).

display dialog boxes from shell scripts

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.

Show KDE dialog boxes from shell scripts

MessagePop is a simple application designed to help you convey a message to the computer user. The program allows you to specify the message text and the other parameters from the command line.

a GTK-based xmessage clone

wxGlade is a GUI designer written in Python with the popular GUI toolkit wxPython, that helps you create wxWidgets/wxPython user interfaces. At the moment it can generate Python, C++, Perl, Lisp and XRC (wxWidgets' XML resources) code.

create a menu to run commands

Gtkdialog is a small utility for fast and easy GUI building. It can be used to create dialog boxes for almost any interpreted and compiled programs which is a very attractive feature since the developer does not have to learn various GUI languages for the miscellaneous programming languages.

My problem was that the KDialog code is still not ported to Qt5 and it depends on various Qt4/KDE4 components. The kdialog has big dependency sizes so we made an alternate dialogs like kdialog switches, options. We would still like full compatibility with kdialog but a few options are still not finished and although this release provides many important functions. Full Python Qt5 base! Not dependent on KDE or any desktop environment.

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. with the treeview, the file selector, the edit box, the range box, the help button/box). Because Xdialog uses GTK+, it will also match your desktop theme.

wxDev-C++ is an extension of Bloodshed Dev-C++ by Colin Laplace et. al. This program helps you to create dialogs and frames for wxWidgets visually using a form designer. With all the wonderful features of Dev-C++, wxDev-C++ is still being actively developed. The main aim of this project is to provide the wxWidgets community with a free, open-source, commercial-grade IDE/RAD tool for development with wxWidgets.