More CPUs!

http://www.arduino-avr.com/ has a large list of Atmel chips that have been tested with the Arduino IDE.

Information on the cores is also available.

Tiny Arduino Core!

[Coding Badly] has released his ATtiny84 core for arduino.

http://code.google.com/p/arduino-tiny/

Features:

• Support for all 10 digital pins
• Support for all 4 PWM pins
• The three analogReference modes work
• NewSoftSerial works
• Burn Bootloader can be used to change fuse settings

Limitations…

• Serial is an empty stub.  A Sketch that references Serial compiles but method calls do nothing but return.

Caveats…

• tone may not generate the correct frequency.  We need a few more people to test.

Via the Arduino Forum