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.

via Arduino – HomePage.

2009.03.11 Arduino 0014 for Windows and Mac OS X available from the software page. This is a minor bug fix release.
Arduino Software Release Notes

0014 – 2009.03.07
[core / libraries]
* Fixing bug that prevented multiple outgoing Client connections with the
ethernet library.

[environment]
* Clarifying ATmega168 vs. ATmega328 in the Tools > Boards menu.

[tools]
* Updating the Mac OS X AVR tools to AVR MacPack 20081213. This includes
avr-gcc 4.3.2, which should fix problems with functions called from
within interrupts.

Not sure how exactly I came to miss this, but the newest Arduino IDE is out.

Version 0013

Windows, Linux (32 Bit), Mac

Biggest bonuses:

- Printing Floats

- Reduced Sketch size by not including unused functions

- Support for ATMega328, which is basically a 168 with double space.

From the release notes:

0013 - 2009.02.06

[documentation / examples]
* Adding examples for Parallax Ping Sensor and Memsic 2125 accelerometer.

[core / libraries]
* Adding support for printing floats to Print class (meaning that it works
  in the Serial, Ethernet, and LiquidCrystal classes too).  Includes two
  decimal places.
* Added word, word(), bitRead(), bitWrite(), bitSet(), bitClear(), bit(),
  lowByte(), and highByte(); see reference for details.
* Working around problem that caused PWM output on pins 5 and 6 to never go
  to 0 (causing, for example, an LED to continue to glow faintly).
* Removing cast macros, since function-style casts are a feature of C++.  This
  should fix contributed libraries that broke in Arduino 0012.
* Modifying pulseIn() to wait for a transition to start timing (i.e. ignoring
  any pulse that had already started when the function was called).
* Fixing bug in random() that limited the ranges of values generated.  Thanks
  to Mikal Hart.
* Modifying delay() to pause for at least the given number of milliseconds.
* Fixing bug in Ethernet library that interfered with use of pins 8 and 9.
* Originating each outgoing network connection from a different port (in the
  Client class of the Ethernet library).  Thanks to Paul and joquer.
* Updating ATmega168 bootloader to work with standard distributions of avrdude
  (responding to signature requests made with the universal SPI command) and
  correctly store EEPROM data.  Thanks to ladyada.
* Adding support for the ATmega328.  The upload speed is 57600 baud, so you
  may need to edit boards.txt or reburn your bootloader if you bought an
  ATmega328 w/ bootloader from adafruit or other supplier.

[environment]
* Omitting unused functions from compiled sketches, reducing their size.
* Changing compilation process to allow for use of EEMEM directive (although
  not yet uploading EEPROM data).