Apple has released a beta version of iTunes 11.1 with support for iTunes Radio, Apple's new Pandora-like music streaming service. The beta has a build number of iTunes 11.1b44.
The service is supported by advertising, though subscribers to Apple's $24.99/year iTunes Match service receive ad-free listening.
iTunes 11.1 Beta 1 is available via Apple's Developer Center, though it's currently only available in the United States.
Article Link: Apple Releases iTunes 11.1 Beta 1 to Developers, Includes iTunes Radio