Version 0.7 of leJOS NXJ is out!
leJOS NXJ is a full-blown mature Open Source Java platform for the NXT with a Java Virtual Machine that runs directly on the brick.
The new release
"includes a Windows installer to make installation a breeze for new users (the compressed-file distribution is also still available). New features include better USB support, no more using a paper clip to upload firmware, faster garbage collection, three new GUI tools, a brand new Tutorial, support for many new sensors, bug fixes and much more."
There's also preliminary support for mobile phone remote control and Monte Carlo Localization.
It's decidedly worthwhile to have a look!