With the advent of Windows 95, Microsoft took the ability to edit environment variables and buried it in an obscure part of the system configuration, known only to the chosen few. To make matters worse, the dialog used to edit/display environment variables is too small and can’t be resized. The linked application, Redmond Path, makes it very easy to modify one particular environment variable: the system path.
Update: It appears they’re also developing a utility with which to manage the other environment variables. It will be available here when completed.