I’m often asked about sources for parts, and it always comes up when my friends and I do our Teslapunk panels.
Our two favorite sites are Sparkfun and Adafruit. Each has it’s own strength and weaknesses: Sparkfun is closer for those of us in the West (they’re in Denver) and while they have a large selection of parts for the electronics Maker, they focus a bit more on robotics. Adafruit (based in New York) is an amazing company that was worked hard on bringing a curated selection of products to the Maker community, and produces their own versions of the Arduino microcontrollers: the Gemma, designed to be worn in clothing and the Trinket/Trinket Pro, which are much smaller than the original Arduino. I discussed both the Gemma and Trinket in my post “But the Arduino is too big for my project.” Adafruit also sells the Neopixel product line of programmable RGB (Red/Green/Blue) LEDs available in variously sized rings, strips, and individually. These are the multi-colored LEDs that Thadius Phule (Peter Valentine) uses in a number of his gadgets. I also buy my Lithium batteries from Adafruit.
For generic electronic parts I check both DigiKey and Mouser, but I also check ebay. Buying through ebay can save you a lot of money if you’re willing to wait while they’re shipped from China, but if you don’t get exactly what you expect, you can be SOL. I’ve generally had good luck, but I’ve stuck with components (LEDs, battery cases, etc) and not full Arduinos. Peter does use ebay for his Arduinos and has had good luck.
More to come!