Brads Electronic Projects Forum

http://en.wikipedia.org/wiki/Capacitor
http://en.wikipedia.org/wiki/Inductor
http://en.wikipedia.org/wiki/Resistor
http://en.wikipedia.org/wiki/Transistor

http://en.wikipedia.org/wiki/Integrated_Circuits
http://en.wikipedia.org/wiki/Logic_gates
http://en.wikipedia.org/wiki/Microcontroller

(Please keep in mind that anyone can edit Wikipedia so there may not be the most professional explanation of electronics.)

I've used wikipedia before, they generally seem to be pretty good.