The Eclipse plugin for the most recent version 0.5 of leJOS NXJ, the Java platform for the NXT, is available now.
Integrated into the popular Eclipse platform, it allows for uploading the firmware and developing, compiling and uploading leJOS NXJ programs to the brick. With a lot of bug fixes and enhancements, it supports the most recent Eclipse version 3.3 (Europa) on Java 6, thus runs on Windows and Linux.
For installation and usage, consult the according entry in the News section of the leJOS homepage.
Please direct feedback and questions either to the author (me) or to the leJOS forum.