From the software page: http://arduino.cc/en/Main/Software
[documentation / examples]
* New communication examples (w/ corresponding Processing and Max/MSP code) by Tom Igoe.
[core / libraries]
* Adding support for the Arduino Pro and Pro Mini 3.3V / 8 MHz w/ ATmega328.
* Adding support for the LilyPad Arduino w/ ATmega328.
* Adding write(str) and write(buf, size) methods to Print, Serial, and the Ethernet library Client and Server classes. This allows for more efficient (fewer packet) Ethernet communication. (Thanks to mikalhart.)
* Improvements to the way the Ethernet library Client class connects and disconnects. Should reduce or eliminate failed connections and long timeouts. (Thanks to Bruce Luckcuck.)
* Optimizing the timer0 overflow interrupt handler (used for millis() and micros()). Thanks to westfw and mikalhart.
* Fixing bug that limited the bit() macro to 15 bits. Thanks to Paul Badger.
* Adding ARDUINO version constant (thanks to prodding from mikalhart).
* Ordering the items in the Tools > Board menu.
* Adding "Copy as HTML" command to the Tools menu.
* Eliminating (maybe) the occasional "Couldn't determine program size" errors. Thanks to the Clever Monkey.
* Moving selection of Linux look-and-feel into the arduino script so it can be changed by users. Thanks to Eberhard Fahle.
* Adding automatic dependency generation to the Makefile. (Lars Immisch)