This is a comprehensive list of links to worth reading resources on the interent that I have found during my explorations.
It's worth reading the content of the official Arduino web siteweb site.
Here you will also find the download for the software development environment.
Don't miss the Playground that contains a lot more interesting projects and hints. If you use the search field on this site you will find all: official information, reference information and community added content.
The Blog will keep you informed.
There is also a store for buying the official boards and you can also sell your work there if you want.
Adafruit Industries is a company in New York that is very acive in creating new projects and making cool stuff available in their shop.
A very comprehensive collection of Arduino compatible shields is availabe at
... just to name a view. Be sure to contact your local shop too.
A lot of Arduino related components are also sold on eBay!
A very important source for information is the official specification for the microprocessors used with Arduino. The documentation for the ATmega328P microcontroller can be found at: http://www.atmel.com/dyn/resources/prod_documents/doc8271.pdf.
A good collection of links is available on http://www.freeduino.org/.
Nice drawings of the Arduino UNO and Mega 2560 at: http://blog.makezine.com/archive/2010/12/nice-drawings-of-the-arduino-uno-an.html
The famous tutorial from Limor Fried (Lady Ada) can be found at: http://www.ladyada.net/learn/arduino/index.html.
A German translation can be found at: http://www.freeduino.de/books/arduino-tutorial-lady-ada.
The EAGLE PCB Design Software from cadsoft is an easy to use, yet powerful tool for designing printed circuit boards.
A good tutorial for creating shields can be found here.
Some tips from Sparkfun at: http://www.sparkfun.com/tutorials/108.
This page is part of the http://www.mathertel.de/ web site.