Microsoft announced the availablity of a new NAS offering in the Windows Server 2003 catalogue called WUDSS 2003. It includes "new features such as the Microsoft iSCSI Software Target technology, a new and revised storage server setup experience, new integrated share and storage management snap-ins". It is available now with the Dell PowerVault NX1950 and other OEM’s are expected to follow soon.
There is some further documentation from Microsoft here: