The 5th major iteration of the Camera Raw plug-in is now shipping as part of Photoshop CS4.  Camera Raw 5 has a number of new features:

• Local adjustment brush
• Graduated Filter
• “Post Crop” Vignetting
• Opacity for the cloning/healing tool
• Improved Auto Adjustment
• Support for the new Camera Profiles that are still in beta form

The Camera Raw code is the ‘engine’ that drives the non-destructive adjustments in Lightroom’s Develop module so you’ll see that the two products are now aligned in terms of image adjustment capabilities.

Camera Raw 5.0 is installed automatically with Photoshop CS4 so there’s no update process beyond installing Photoshop.  One important note is that the new camera support added in the last Camera Raw update for CS3 is not currently available in Camera Raw 5.0.  Adobe will be providing a Camera Raw 5.1 update next week that will include additional camera support.

Source: http://adobe.com