Adobe introduced updates to Photoshop, Bridge, and Lightroom that address a large number of items. First, there's the obvious thing for Nikon users: Photoshop CS3, Bridge CS3, and Lightroom now support the new Nikon DSLRs (D3 and D300) raw file formats.
However, that's not the big news with these updates. For Photoshop, the big news is that the desktop printer problems many of us experienced in the CS2 to CS3 change have been addressed. Windows users who had Epsons tended to be the hardest hit by the myriad of minor printing problems CS3 introduced, but even Mac users with other printers struggled with minor issues. (Hopefully) all gone now. Adobe has a five-page PDF file labeled "Printing Notes" that explains how the changes and how to use them. This is a must-read for anyone who prints from Photoshop CS3 (as is the 10.0.1 update).
Lightroom got a bug fix update, including fixes that allow it to run under the new Mac OS X version 10.5 just introduced.
The Adobe Updater on your computer should find all the updates. For those of you looking to just update ACR, see the Photoshop Family page and look for the "Camera raw support" link.