I would recommend the tutorials on Sparkfun ( http://www.sparkfun.com/tutorials/57 ) to get you started with microcontrollers.
In short, resistors are devices that turn electrical 'energy' into heat. Capacitors are devices that store voltage or charge. Inductors are devices that 'store' magnetic fields. Diodes are devices that restrict current in a certain direction similar to a one-way valve. Now these are very basic simplifications of electrical components and there are many variations of all these device.
A ground is a place of common voltage and is a reference point which is usually close to 0V. Voltage is potential difference not absolute values so when measuring and notice you have 5V with reference to ground. 'Ground' could technically be at an arbitrary voltage, let's say 1V, making the actual voltage at the positive probe 6V. The reason it is called ground or earth is because at some point in the circuit, perhaps back at the power station or near the meter, the wire is actually connected to the ground. I'm not exactly sure of this next part so don't quote me on this but from my understanding the reason the ground is 0v is because the Earth can dissipate an 'infinite' amount of voltage because it is so large. The charges will try to spread as far apart as they can around the surface of a sphere ( earth ) and just because it's so large it is 0 at our point of contact. Anyways, don't get caught up on whether ground is truly 0 or not. One other practical application for grounds is for safety to protect consumers from discharge of high voltage. For instance all metal cases of appliances are grounded. If for some reason a 120V line became lose and touched the case ( which we're pretending is not grounded ) and you came by an touched the appliance. The 120V would find a path to ground through you and could cause internal injuries. If the case is grounded the 120V is 'shorted' ( I'll explain later) to ground and this will likely reset a breaker on your houses panel removing power from the device and keeping you safe if you touch it.
Some other key terms for learning electronics:
Series is when devices are connected one after another. All devices have the same current because there is only one path however voltage is different accross each depending on it's position in the series.
Parallel is when devices are connected to the same two points. All devices have the same voltage but the current is split between each path between the two points based on the resistance.
Short or short circuit comes from the idea of taking the shortest path. This is actually the result of a parallel circuit. The 'short' path is the path with the least resistance and thus the most current. Usually you would burn the wire or whatever was shorted which is why these scenario's are dangerous and often teh start of fire or in the case micro controllers the frying of chips
Open is just when there is a break in the wire or circuit preventing the flow of current.
Understanding the fundamental devices and these key terms should allow you to understand basic circuitry.
So i'm not sure how much back ground you have in electrical side, but hopefully that was helpful. Anyways on to microcontrollers.
I can't really explain microcontrollers without going into semiconductors, VHDL, finite state machines, but basically a microcontroller is just a little computer. It has memory and a processor on in a single package. If you think of your big CPU in your computer a microcontroller is just a much much more basic version of that.
EPROM ( Electronically Programmable Read Only Memory ) . I agree it's a weird name because if it's programmable it's not read only but it has to do with being programmable and read-only at different states so both words are valid. There is EEPROM which the first E is erasable with High-Voltage from external source or sometimes from UV lights. I don't know much about this other than that but it's basically just another memory region for things that will remain constant during normal operation of the device so if you have something that will enver change you could put it in EPROM to free up some RAM space.
You said ages ago. lol there are still PICS and they are still quite popular and the main contender to AVRs ( Arduino / ATmega328 ). PICS are just different style of microcontrollers that have different feature sets and different memory styles.
If you want to load code onto a microcontroller you need to follow those tutorials i recommended or look at the datasheet for the device and get it in a development board ( oscillators, decoupling caps, and power etc. ) Then you can use an ISP ( In System Programmer ) such as the AVR ISP MK II.
As a matter of fact i'm trying to create a post to teach you this exact skill of getting code originally written for Arduino onto a basic ATmega328 in my post here:
However your idea of scrapping IC's from toys is not very practical in my opinion. Each toy manufacture will use a chip specifically designed to be most economical for that toy based on I/O, memory, speed, etc.. There are thousands of variations of chips and the time it takes you to figure out which chip they used if you can even get it out without damaging it and then setting up a whole new development board for that chip each time is not feasible. Also ATmega328 chips which are used in the UNO's are only about 4 dollars so it would be much much better IMO to just become very familiar with these and then branch out to more capable chips in the future.
Hope that helps, my hands are tired of typing :)