Xdialog [chez.com] is really quite slick. It can take any shell script that uses Dialog and turn it into a GUI application. It is really simple to use, you just drop in Xdialog in place of dialog and it does the rest for you.
What is Xdialog? 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.