While I was on vacation, Microsoft pulled a fast one and released SP1 for WSS 3.0 and MOSS 2007 earlier than expected.  Of course, SharePoint Designer 2007 was also service packed along with the Office 2007 SP1.

The key points in SP1 for SharePoint Products and Technologies are:

• Support for installation on Windows Server 2008
• ASP.NET AJAX compatibility and support (If you were an ASP.NET AJAX developer, you could do it before, but it was not officially supported.)
• New stsadm.exe operations and properties
  • mergecontentdbs - Permits a site collection to be moved from one content database to another.
  • renamesite - Changes a URL of a host-named site collection to a new URL.
  • peoplepicker properties - Provides setproperty and getproperty operations to define the scope of the People Picker Web control to an Active Directory® directory service organizational unit.

Also, of considerable note in the Technet document about SP1, is the final recommendation for 64-bit hardware for SharePoint deployments.  It is officially reiterated that this version of SharePoint is the last to have support for 32-bit (x86).  So, if you haven't already gone to 64-bit , start planning and budgeting for the shift.

To install SP1:

1. Install WSS 3.0 SP1
2. Install WSS 3.0 Language Pack SP1
3. Install MOSS 2007 SP1
4. Install MOSS 2007 Language Pack SP1

On SPD 2007 clients:

1. Install SharePoint Designer 2007 SP1
2. Install SharePoint Designer 2007 Language Pack SP1

Also, there is a WSS 3.0 with SP1 (slipstreamed) install available from Microsoft Downloads in x86 and x64.

Be aware, that installing SharePoint (WSS or MOSS) on Windows Server 2008 requires SP1.  Until Microsoft provides slipstreamed bits for MOSS 2007 with SP1, installation can be a bear.  I highly suggest you take a look at Ben Curry's blog post on installing MOSS 2007 SP1 on Windows Server 2008.