Are there personal  Dashboards for each User? If not create them
first. Once you have the personal dashboards in place, routing to a
user specific dashboard can be coded in default page  of IIS.

Unfortunately, no, there are not personal
dashboards for eacgh user. Let's say that a particular user  wants to
say that his or her homepage is a second or third sub-category or
child folder in the Document Library. How would that make that sub-
dashboard (or any dashboard for that matter) their home  page? Or, if
that is not possible, could I designate what the home page  is
according to which security group they belong to? Sales? Developers?
Research? etc.

If you don't mind, can you be more clear on your
requirements?

To create personal  dashboards, please see my posting
on SPSFAQ.com. Here is the link,
http://www.spsfaq.com/customising.asp?postid=96

Typically, when one logs in they go to the "Home
Dashboard" Let's say a certain user  who, for example, usually has to
then drill-down to a sub-folder in the document library to import new
documents. So, after signing in, from the Home Dashboard, they have
to click Document Library -> Documents -> Parent Folder Name - >
Child Folder Name (or what ever the case might be). How could they
just force that child folder to be THEIR Home Page, so they do not
have to do the drill-down? let me know if that does not make sense..
and thank you...