When you develop Sharpeoint solutions in Visual Studio, there is one tool you can't miss: WSP builder.

The description from codeplex: The WSPbuilder is a console application that creates SharePoint Solutions files
based on a folder structure. WSPBuilder will automatically traverse a "12" folder structure
and creates a SharePoint solution manifest.xml and the wsp file based on the files it finds.
Therefore you do not need the knowledge of how to create a solution manifest.xml
and wsp file any more.

The link to download: http://wspbuilder.codeplex.com/