In Windows, when saving a file for the first time you are presented with a list of icon choices to the left side of the “Save As” dialog box. Those icons include My Documents, Desktop, Recent Documents, “My Computer” (or whatever yours is called). (I’m sure that those icons can be modified, too, but I haven’t had to do that in so long that I’ve forgotten how. I think you can add—one or two—icons of your own for other locations, or replace the defaults with your own.)
What I have done is set up a folder of shortcuts to folders that I use all the time: a set of folders for “Proposals”, another set for “Contracts” and a set for “Department”, as well as numerous other locations throughout my system and my network.
So whenever I have a “Save As” dialog, I click to My Documents and from there to the folder for “My Shortcuts” ... and go wherever I want. So in three clicks I can be at nearly any folder in my system that I routinely save to. And modifying that list of shortcuts is a breeze, because I know where they’re all stored (in My Documents \ My Shortcuts)—and I just make new shortcuts as the need arises. I also archive my old and unused shortcuts, for the times when “Proposals” over time turn into “Contracts”, for example.