The Eclipse Project has posted the first release candidate of Eclipse 3.0, an open source integrated development environment (IDE) for Java. It also doubles as a base platform for your own applications, an alternative to the AWT and Swing, and a powerful floor wax and dessert topping. RC1 is a pure bug fix release. There are no new features since M9. Linux, Windows XP, Solaris 8, AIX, HP/UX 11i, or Mac OS X 10.3 or later is required. Earlier versions of Mac OS X are not supported. Earlier versions of Windows may work but are not tested.
I'm told that IntelliJ's early access program has now posted build #2057, which is compatible with Apple's Java 1.4.2 Update 1 devloper preview 2.