MakeDDF Version 1.0.0
Normally, Sharepoint Development feels quite "modern": You write your stuff with .net 3.0 and add some XML and XSLT into the mix. But then, you have to take a little trip back 20 years when it comes to creating the .wsp file for your solution, using makecab.exe and a .ddf file.
DDF Files are not only unlike any other standard file format, they are also somewhat complicated when it comes to subfolders. In order to ease the work of creating .ddf files a bit, I made a small command line tool called "MakeDDF" which allows you to specify a directory and it will create the .ddf file that contains all the files in that directory. The resulting file can then be passed to makecab /f to create your .wsp file a bit more painless than useful.
It's freeware and requires the .net Framework 2.0, get it from here.