These links go to youtube videos that give great explanations of the fundamental physics behind inductors. It is critically important to have a good feel for what these components do, not just be able to solve the arithmetic equations that describe them.
This intro to inductors starts with a cat. It is one of the best, from afrotechmods
Another look at inductor basics, discussing actual components and such from afrotechmods
A great video on ultra capacitors, also from afrotechmods on youtube.com
A video that shows building inductors and demystifies them.
A description with animated drawings that shows current and magnetic fields.
Operational Amplifier Links
This is a nice intro to op-amps from a prof at U Oregon. Very clear descriptions of basic op-amp circuits.
A wild and crazy op-amp page at Stanford. Good stuff and some links to other good op-amp sites.
This link points to an operational amplifier pdf document produced by Texas Instruments, Co. It is entitled "Op-Amps for Everyone" in a bit of whimsey, I guess. http://www.ti.com/lit/an/slod006b/slod006b.pdf
A youtube tutorial on a simple way to understand most op amp circuits.
A second, clear explanation of how to analyze even fairly complex op amp circuits.
Another youtube talk, somewhat lengthy and definitely quirky, but fairly clear.
Graphene, Material of Future Circuits? Link
MIT's Center for Bits and Atoms A neat brainstorming place with lots of strange ideas
Fritzing is "an open source hardware initiative that makes electronics accessible as a creative material for anyone. We offer a software tool, a community website and services in the spirit of Processing and Arduino, fostering a creative ecosystem that allows users to document their prototypes, share them with others, teach electronics in a classroom, and layout and manufacture professional pcbs."
Design a circuit, and Fritzing will enable you to produce small run (like 1) circuit boards that are completely professional in appearance.
Arduino is another open source initiative that enables easy access to microprocessor-based electronic systems at very low cost.
"What Arduino can do
Arduino can sense the environment by receiving input from a variety of sensors and can affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is programmed using the Arduino programming language(based on Wiring) and the Arduino development environment (based on Processing). Arduino projects can be stand-alone or they can communicate with software running on a computer (e.g. Flash, Processing, MaxMSP).
The boards can be built by hand or purchased preassembled; the software can be downloaded for free. The hardware reference designs (CAD files) are available under an open-source license, you are free to adapt them to your needs."
PSpice is a circuit simulator that is the industry standard for modeling performance of electronic systems. Cadence produces high end circuit capture and analysis programs that are based on Spice.
Some electronic component retailers. The catalogs from these folks are free, and are great browsing resources for getting a feel for the range or electronic devices that are available.
"Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required."www.electronics.stackexchange.com
Four major, general purpose electronic suppliers first, Mouser, Digikey, Allied, and Newark.
Lots of solar cells and related components here.