With the release of the new Arduino MEGA, we have a new version of the IDE.

Download the Windows, Linux or MAC OS X verison.

Release notes:

0015 – 2009.03.26

[core / libraries]
* Adding support for the Arduino Mega (ATmega1280).

[environment]
* Reinstating use of core.a library in the build process, slightly shrinking
compiled sketch sizes. (Thanks to William Westfield.)
* Fixing bug in copy for forum (thanks to eried).

Overview of the new Arduino Mega:

The Arduino Mega is a microcontroller board based on the ATmega1280 (datasheet). It has 54 digital input/output pins (of which 14 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. The Mega is compatible with most shields designed for the Arduino Duemilanove or Diecimila.