I wrote a simple program using PyQt4 and Speech Dispatcher.
I wrote it for understanding how to work with PyQt. I used Qt4 Designer to design the UI and the program loads the UI file at run-time.
Before you can really use this program, you have to make sure Speech Dispatcher really working. I have to set the output device of each module to PulseAudio, somehow, ALSA doesnt work. For festival module, I also need to start the server with these files.
You can see and download the source here. The speak.py is the main program. Its licensed under the GPLv3.