Thanks again to Rob for putting these words together on the different versions of packages in the cumulative updates – specifically describing the additional options available since the December 2008 Cumulative Updates which introduced the server rollup packages. Over to Rob:
The Server CU is released in two different versions. The first version is in Individual Packages specific to a particular product like WSS, Project Server and MOSS. If you do not have MOSS installed and have already installed the Infrastructure Update for Office Servers then you can download and install these individual packages.
The second version is the Server Rollup Packages. This is a set of two uber-packages which contains all the fixes for WSS, Project Server and MOSS. These packages should be used when MOSS is part of the deployment or Infrastructure Update has not been deployed to the server environment. The Server Rollup Packages are much larger (~200MB each) but they will greatly simplify MOSS patch deployment.
The Server Rollup Packages include all of the fixes included in the Infrastructure Update so installing these packages will allow you to skip the added step of deploying the Infrastructure Update. The Infrastructure Update only needs to be installed once so this will not be a consideration for deployments that already have the Infrastructure Update installed.
More general information and links regarding Project Server Cumulative Updates and their deployment can be found at http://technet.microsoft.com/en-us/library/dd239177.aspx.
At the time of writing the February update is the latest and more details are in the post at http://blogs.msdn.com/brismith/archive/2009/03/13/project-server-2007-cumulative-update-for-february-2009.aspx.