Paul Thurrott has published some information on the Windows Vista Product Editions

There will be two general categories of Windows Vista editions, which map closely to the two that exist today for XP ("Home," which comprises Starter, Home, and Media Center Editions, Pro, which includes Professional, Professional x64, and Tablet PC Editions). In Windows Vista, the two categories are Home and Business. In the Home category, Microsoft will create four product editions: Windows Vista Starter Edition, Windows Vista Home Basic Edition, Windows Vista Home Premium Edition, and Windows Vista Ultimate Edition (previously known as "Uber" Edition). In the Business category, there will are three editions: Windows Vista Small Business Edition, Windows Vista Professional Edition, and Windows Vista Enterprise Edition. In all, there are 7 product editions planned for Windows Vista

Windows Vista Product Editions Revealed