Good arduino projects require documentation.
Free documentation is even better !
Some well known arduino resources
Free online tutorials for arduino :
- Arduino official tutorials
- Ladyada tutorials
- TronixStuff tutorials
- Sleep dog Guides
- flossience arduino tutorial
- Arduino Programming Notebook
- The Complete Beginners Guide to the Arduino from EarthShineElectronics
- Getting Started with Arduino (Massimo Banzi) - The first edition of this one is free, but the newest edition offers more and isn't that expensive
Keep in mind that the documentation is the number one for hardware and software engineering.
The list is not complete please contact us if you have some valid links.