Microsoft has released Service Pack 1 for Windows 7 and Windows Server 2008 Release 2 for download. This overview page provides links to documentation for the Service Pack; mostly, it is a roll-up of previous security patches and hot fixes. You can get the actual Service Pack from Windows Update (recommended for single-machine updates), or from this download page.
Given that this is mainly a roll-up of previous updates, you might want to wait a couple of days before installing the service pack, if you are confident that your patching is up to date. You should definitely plan to do it, but these mega-patches sometimes have unexpected issues, which tend to surface fairly quickly.