I am writing [have written] an Arduino core for the Attiny13.
It will [does] support a subset of the Arduino functions and is of relatively small size.
So far it seems to work but I have not tested it completely.
I have not tested it thoroughly
and I only tested it with 128khz internal oscillator
Supports 128KHz, 600KHz, 1MHz, 1.2MHz, 4MHz, 4.8MHz, 8MHz, 9.6MHz, 10MHz, 12MHz and 16MHz clock speeds (Although not all are tested) - More frequency support soon
If anyone gets a chance give it a try.
Although programming a microcontroller with this little flash space with a Arduino core is alittle impractical, it helps the beginners greatly. Core13 is optimized for size so you have more space for user code.
For the most part, I read the Arduino core source code and rewrote most of it from scratch.
It may work for other 8 pin Attiny series but I cannot promise.
Currently supported functions:
* = Partial support
edit: fixed bugs and attached new version.
edit: Added support for 4, 4.8Mhz and improved support for 9.6Mhz
edit: Released 0.15 that fixes bugs
edit: Released 0.19 and removed old version attached. Please download from sourceforge(If you cannot download from SF (like because their site bloat hangs your machine then PM me and I can provide a direct download)
Supports the old Arduino IDE (pre-1.0) and Arduino 1.0.x. Support for Arduino 1.5 is untested and may not workFrom now on download from sourceforge.net for the newest release http://sourceforge.net/projects/ard-core13/
Licensing note: Core13 is under a mixed license (as marked at the top of each source file) this is because I included
some Arduino core files. Most of the code is under a very unrestricted license while a few files are under the standard Arduino core license