Hey Guys I'm a semi pro learning working with PIC MCU's. I was looking into oscilloscope's and see the sound cards ones for very cheap. I know its not going to be like a real one. But are these at all usable? I really don't critically need one, but would like to have a cheap one if possible. Would it be worth getting one for $30 or so?

 

They're really only useful in the audio spectrum. The sample rate is just too low for much else. It's better than nothing, certainly.

If you'd like to try your hand at building a buffer yourself (some protection for your sound card), here's a project page:
http://xoscope.sourceforge.net/hardware/hardware.html
And you can download Winscope freeware from this page:
http://www.mitedu.freeserve.co.uk/Downloads/download.htm