A program with a GUI has been developed (fft_spectrum_gui.py). It uses the Tkinter library, basically because it is the one included with Python, and no additional programs are needed. Also, it integrates very well with matplotlib.
The new program combines the programs acel_file_plot_03.py and serial_avr_01.py. This new interface lets you scan serial ports, select the serial port, save the sampled data to file, and open files with sampled data previously saved. It also has a scrolled textbox where messages are displayed (the ones printed on the previous programs).
A screen shot is shown below.