The LEGO support page has been updated with downloads for dynamic blocks, mini blocks, and RCX support.

Dynamic Block Update
The Dynamic Block Update allows the MINDSTORMS NXT Software to import new blocks to the Complete palette. These blocks include the Mini Blocks, the Legacy Blocks, 3rd party sensor blocks or any other blocks developed using the LabVIEW Toolkit for LEGO MINDSTORMS NXT.

Mini Block Library
The Mini Block Library adds 4 new blocks to the Action palette: Mini Move, Mini Motor, Mini Display and Mini Sound. These blocks are very similar to the blocks that were in the 1.0 release of MINDSTORMS Software, but they have been optimized to make smaller programs on the NXT.

Legacy Block Library
The Legacy Block library adds support for RCX actions and sensors to the LEGO MINDSTORMS NXT Software. There is a new block for the RCX motor, lamp, touch sensor, light sensor, rotation sensor and temperature sensor. NOTE: In order to connect the RCX sensors to the NXT, a converter cable is required.

[via The NXT Step]