Microsoft had released the Windows 7 SP1 to MSDN users last week and it has been made available to regular customer starting from February 21, 2011.
Most of the Windows 7 Service pack updates have already been released as patches earlier on and the SP1 would help you apply all those updates if you haven’t done so already in the past. Service Packs are also used by administrators to deploy patches across a large number of PCs at once.
If you are looking to download the service pack 1 for Windows 7, you will receive it through the Windows Update. However, you can also download and apply the Windows 7 SP1 and Windows Server 2008 SP1 directly to your PC by visiting this Microsoft Download Link.
The download size of the files are pretty large, so you might just want to wait for Windows Update to ship the service packs to you.