Here are some of the most useful sites I’ve found for Arduino related projects and tutorials.
- Arduino.cc – duh, good reference for the language and libraries
- Fritzing - visualize your hardware AKA prototyping software! I use this for all the circuit diagrams on this site.
- Adafruit Industries – not only do they sell hardware but their tutorials are fantastic
- Lady Ada – Limor’s site loaded with projects- it’s the sister site to Adafruit
- MegunoLink – MegunoLink is a free tool for talking to any microcontrollers (or any serial device for that matter).
- Arduino Uno R3 Details – Nick Gammon goes into fantastic detail explaining what each of the major pins/groups do in this post along with links to more details about the protocols and such (SPI, I2C, ICSP etc)