A few days ago, Microsoft has released Service Packs 1 for SharePoint 2010. As usual, the installation must follow general rules of installation order:
1. SharePoint Foundation
2. SharePoint Foundation Language Packs
3. SharePoint Server 2010
4. SharePoint Server 2010 Language Packs
And if you have SharePoint Server 2010, you can run SharePoint Configuration Wizard after completing installation of all service packs. You can skip SharePoint Configuration Wizard on installation order 1-3.
If you have multiple servers in a farm, make sure that you have perform the installation in all servers before kicking-in SharePoint Configuration Wizard in the server.
More information from the team blog : http://sharepoint.microsoft.com/blog/Pages/BlogPost.aspx?pID=984