Here are some of my favorite sources of information, useful projects and supplies.
Surplus electronics and mechanical parts:
Jameco, supplier of new and surplus electronic parts. A great selection for those that want reasonably sophisticates parts but aren’t ready to tackle Digikey or Mouser yet.
P&T Surplus, my favorite place for metal, glass, old electronic curiosities, pneumatics, and more.
New electronic parts:
Digi-Key, Mouser, Allied, Future, Newark: big giant warehouses with millions of parts. Not millions of units, millions of different parts. They can be intimidating, but they have reasonable search functions on their websites. Don’t be afraid! If you make a mistake, it will only cost you a dollar or three anyway.
suzohapp: Buttons? Yes.
Kits, breakouts, useful components, maker supplies:
Sparkfun, Adafruit, Makershed: these are the best places for budding makers to get friendly and well documented goodies from sensors to speakers to signal diodes to silicon solar cells! Also things that don’t start with an ‘s’.
Information, in paper form:
Nuts and Volts magazine, lots of great beginner projects involving microcontrollers, electronics, radio, and related technologies.
Anything by Forrest Mimms, especially Getting Started in Electronics. These are the books I had as a kid, and I still have my copies.
Practical Electronics for Inventors, by Paul Scherz. A clear, well illustrated and broad introduction to electronics. Great reference, and well written too. A must have! I still crack this all the time.
Arduino!!!!! The best possible way to start in micro controllers. World famous!
Teensy: a mini version with more capability and less price. Pretty good deal! Slightly less easy to use than the standard version, and shields don’t fit, but great otherwise. Comes in several great flavors including ARM and AVR.
Services and design tools:
EAGLE, a powerful (if a little infuriating) circuit board design tool. There’s a fully functional free version that is only limited in a few small ways, and several tiersof paid versions. Mostly the difference is the maximum size of board you can design.
Fritzing: A visual circuit design service and software. Open source! Great for designers, students, artists and beginners of every stripe.
Advanced Circuits: This is where I get most of my circuit boards made. Manufactures in the USA at very high standards. The also have a free design checker that is very useful.
Gold Phoenix: Cheap and good circuit boards for the brave!