Windows 7 RC is now available for MSDN and TechNet Subscribers. It would be available publicly on May 5.
Source : Windows 7 Release Candidate Is Available From Microsoft: Industry experts advise partners, companies and developers to preview Microsoft’s next operating system.REDMOND, Wash.  April 30, 2009  Today Microsoft Corp. has reached a significant milestone with the Release Candidate (RC) of the highly anticipated Windows 7 operating system, now available for download to MSDN and TechNet subscribers at http://technet.microsoft.com. Broader public availability will begin May 5 on the Microsoft Download Center at Microsoft Download Center. The RC milestone is a result of feedback from millions of customers and partners around the world. It indicates the operating system is entering the final phases of development and is ready for partners to develop new applications, device drivers and services, and ready for IT pros to evaluate Windows 7 and examine how it will operate in their environment.