From what I've seen introductory electronics text & experiments either assume a very modest set of tools with a digital multi meter being the the biggest item or are aimed at a fully equipped lab such as a in a school setting.
I think there should be some tutorial materials that include the use of low-end scopes, both on how to use the scope and how to learn more using the scope.
The analog to digital converters in PC sound cards can be used as a low end scope with a number of significant limitations. If you stick to the audio range I think there are a lot of experiments you could do that would be very educational. Of course you need to be very careful to avoid not blowing up your sound card and/or pc. Note: the input voltage range being audio is very limited around a volt or two. If you are measuring line level audio sources this usually isn't a problem.
Note: the sound card inputs block D.C. so you can't measure D.C. input, (they are coupled through a capacitor which will block D.C. and only pass the A.C. portion of the signal.)
A USB sound card can be used instead of your PC's sound card input so at least if you blow it, you can replace it more easily than your pc or laptops motherboard. I have a Behringer UCA-202. Electronics Express used to sell a couple of usb sound adapters for students.
If you are on windows download the Zeitnitz oscilloscope software. http://www.zeitnitz.de/banned/scope_en
. If you are on Linux you can use xoscope.
You can use software to generate as a signal generator for some test input signals in the audio range. Use software like Audacity to generate sine waves and other wave forms. The Zeitnitz software has a function generator too. Audacity can be used to show the wave forms of recorded sound files (digital samples of the analog). Also you can generate touch-tones, aka DTMF (two tones) and see the waveforms to see how two signals interact.
You can use the oscilloscope software and a microphone to pick up signals. Try whistling, look at the wave form of anything that can make a relatively pure tone.
If you hold the lead for the sound card input in your hand and set the scope controls right you can see how much AC 60 cycle noise your body is picking up.
Just some ideas. Personally I think there is a market for tutorials, books, videos that would teach a little about electronics, audio, signals, sampling, (a/d conversion) etc. using a PC sound card and some very basic components.
Hope This Helps,