Microsoft has released Windows 7 SP1 to MSDN and TechNet customers on Wednesday. The free download allows Windows 7 customers to upgrade their machines to the latest Service Pack.
Microsoft has confirmed the official build for Windows 7 SP1 RTM is 7601.17514.101119-1850. Microsoft will release Windows 7 SP1 to non-MSDN and TechNet subscribers starting February 22, 2011. The update will be available through Windows Updates for existing Windows 7 customers.
More info here.