Visual Subst is a small tool which allows you to associate the most accessed directories with virtual drives. It uses the same API like console "subst" utility, but makes it easier to manage virtual drives in a GUI way.
Personally, I use virtual drives everywhere – I always prefer to press ALT+F1 in my file manager and switch to a project directory where I keep hundreds of various files. Using virtual drives, I can quickly access these files whenever I want to.
Visual Subst does not require installation. It is fully portable because all settings are stored into an INI-file. However there is a simple installer provided which will help you to create some program shortcuts.