What are the best free Python libraries for GUI and signal processing?

[fleem]

I'm going to mess around with some Python and was wondering what free libs I should consider. So far I've got:

GUI - Tkinter
Scientific (mostly signal processing for me) - SciPy

Are these OK? Any opinions? Other libs you like (gaming, sound, hardware control & networking, etc.)

 

[Edgardo]

I recently watched a video of matplotlib here. You can create some neat plots with it.