Apple has released iTunes 8.2, an update that "now supports iPhone or iPod touch with the iPhone 3.0 Software Update." The extremely brief release note also indicates that iTunes 8.2 includes many unspecified accessibility improvements and bug fixes; a security vulnerability involving itms: URLs has also been addressed. It's available via Software Update or as a standalone 77.3 MB download.
What's interesting about this update is the timing, coming one week before Apple's Worldwide Developer Conference (WWDC). The iPhone 3.0 software will be the star attraction, and developers have been working with betas for a couple of months. Could Apple be planning to release the final version of the iPhone 3.0 software to coincide with the event, ahead of a rumored iPhone hardware update? When the iPhone 2.0 software was released on the same day as the iPhone 3G (which was also the day Apple switched .Mac to MobileMe), Apple's servers crumbled under the load of activations (see "iPhone 3G: On the Line in Seattle," 2008-07-13). So I can see the case for separating the software and hardware releases, even if it means owners of the original iPhone and the iPhone 3G get to install the new operating system before new units running it appear.
More likely, I think, is that Apple released iPhone 3.0 compatibility so developers can test live interactions between iTunes and the new software before iPhone 3.0 ships. With a larger share of the market, tens of thousands of developers, and more competition (such as from the Palm Pre, which is due to ship two days before WWDC), Apple doesn't want the same type of fiasco as last year's MobileMe release (see "Apple Claims MobileMe Mail Fully Restored," 2008-07-30).
Also released today was QuickTime 7.6.2, which provides support for iTunes 8.2 and fixes a number of security vulnerabilities related to viewing malformed media types. It's also available via Software Update or as standalone downloads for Mac OS X 10.5 Leopard (57 MB), Mac OS X 10.4 Tiger (48 MB) or Windows (20.9 MB).