CS4 ships

Photoshop CS4 is now available, along with Camera Raw 5.0, a new generation of the Camera Raw pipeline. Version 5.0 doesn't contain all the new camera updates from 4.6, but 5.1 will be released shortly to being them to par.
For Lightroom users, CS4 will automatically replace CS3 in the Edit in Photoshop menu item. To continue to use CS3 from there, you can select it as an external editor (note that an intermediate file is created with external editors).

For more info see Lightroom Journal

Photoshop CS3 Public beta released.

Loads of information over at Photoshop News, along with tutorials and a link to Martin Evenings CS3 book. There is a free download of the first chapter. This does apply to Lightroom in a big way because Camera RAW 4.0 Beta is included and contains features found in Lightrooms Develop Module, including Fill Light, Recovery and Vibrance. Hopefully this will bring XMP compatibility between the 2 programs.
Update Martin Evening has confirmed that his beta (later than 4.1) is compatible with ACR4 and CS3. Tom Hogarty has also indicated that there in still no proper compatibility with B4.1 though.