Knowing these GUIDs will allow you to edit
.csprojfiles to easily change a project type in cases where Visual Studio will not allow using the GUI
With what I blog about in the different areas, new VS versions, etc, I run into this, "Project Type Unknown" all the time. Then I search with the GUID and try to figure out what the actual project type was. In short, I've needed this list for about forever. If you've every had to deal with this too, you'll know the value of this list...