If you're interesting in the Arduino - start here:
http://arduino.cc/
It has a most excellent user forum - very friendly, very helpful, very active:
http://arduino.cc/forum/
The Arduino software platform is completely open-source (and free); the compiler is avr-gcc (C/C++ for AVR), with the main library based on Processing/Wiring; the IDE is also based on Processing and is developed in Java. Some people have been successful using the Arduino core files and such with Eclipse (if you need something more robust than the standard IDE - which is designed to make things simple for users); you can also do everything "standalone" using the compiler, the libraries, and avrdude to upload the binary to the Arduino hardware (which is really just an AVR microcontroller - typically an ATMega328, but there are others in the family that are available - both larger and smaller).
There's some new and exciting things coming down the pipe for the Arduino community - the 1.0 release is expected "real-soon-now"; also Atmel and the Arduino team have announced the impending release of an ARM Cortex M3 (I think that's right) Arduino called the Due:
http://www.atmel.com/dyn/products/v...uino_Atmel.html&category_id=163&family_id=605
So - 32-bit goodness! Note that Atmel DOES NOT make the Arduino (they never have - the Arduino started out as an open-source project to make microcontrollers friendlier for new users and artists; the selection of the ATMega8 for the Arduino was partially due to influence from the Wiring/Processing boards which were based around similar hardware, and the fact that open-source compilers are more available for the Atmel/AVR line).
There have been others in the past that have done similar boards, though - notably:
http://leaflabs.com/devices/maple/
http://www.xduino.com/
**broken link removed**
There's also the fairly new option of Microchip getting into the act (also as a 32-bit platform):
**broken link removed**
I think you have to take some kind of notice that the Arduino is something more than a "fad" when Microchip is "following" - rather than "leading" such a community.
I see it as a good thing; competition and more platforms are always welcome, as long as the open-source availability remains (and no one PC platform is dominant over the others - so much about PIC development is centered on Windows boxes; only a bare minimum of the PIC family is supported by open-source compilers - about the only possible way around this is using Wine or a VM of some sort).