I ported the arduino core to an attiny84. This should work with all attinyx4 chips like the 24/44 and 84.
The Arduino IDE does not support attiny chips. Upload (sketches) is not possible, so I had to change some Java classes of the IDE. The modified Java code supports all attiny chips and all atmega chips.
I plan to publish my sources but since there are modifications in the Java files for the IDE, users have to compile their own IDE.
project details: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236434254