Assuming, you're a novice wanting to get into electronics, and desoldered all your old electronic trash and now have a bin full of components - what's the best way to test all these things out? Any ideas simple circuits for testing/sorting components?
The single, best purchase you could make is to buy a Digital Voltmeter (DVM) which has component functions on it. Many DVMs come with capacitor functions, diode test functions, transistor sockets (NPN and PNP), Light Emitting Diode test sockets, battery test functions (under load). I have an older model, a BK Precision unit which has lasted for years. It is more of a component tester because it has no voltage scales or current scales. I haven't checked on prices lately, but they're probably in the range of $40 to over $100. I prefer Fluke but there are many other brands.
The choice of meter may depend on what the age of your electronic trash is. It sounds like you're recovering 1960 - 1990 vintage parts. Most likely those would be wire-leaded parts soldered to a circuit board. They are still usable. As technology moved on more and more circuits are proprietary, built with custom functions and almost zero documentation. So, it all depends on what you are salvaging. If you are salvaging surface mount parts there are component testers with tweezer-type probes which make it much easier to grab the small parts. However, surface mount parts (resistors, capacitors) are almost unusable after being soldered once, then unsoldered, then reused, soldered again. Surface mount Integrated Circuits can be successfully reused after a bit of practice. For surface mount parts get a newer, more modern soldering station.
I highly recommend taking things apart if for no other reason than to see how something is built !! That will give you hints on how to disassemble things in the future