"No more manually creating the manifest.xml file.
No more manually specifying the DDF file.
No more using the makecab.exe application."
Carsten Keutmann has created a SharePoint Solution (WSP) creation tool to generate solutions automatically. The tool can be downloaded on codeplex here.
"The idea for this tool was that the Solution file (WSP) is simply just a packed that transport files from development into SharePoint. Therefore I was able to build a folder structure that matches the SharePoint folder structure (%Program Files%\Common Files\Microsoft Shared\web server extensions\12) and put my features and other stuff in there and then run a program that traverse the folder structure to build my manifest.xml and WSP file automatically. This saves me a lot of work and time creating the manifest.xml and the WSP file."