To tell you the truth I would by the resource kit from MS Press

http://www.sharepointserver.com/books.html
This link shows some of the books available on SPS.

www.microsoft.com/sharepoint/server/default.asp
is the place to start looking at MS SPS.

Here is a quick breakdown that might help.
Workspaces - contains all the files, documents, settings and processes
to create a portal, do indexing and searching and manage documets. You
may have multiple workspaces  on a SPS Server. Each workspace contains
exactly 1 portal. This portal is configured for the intended users  of
the workspace. The workspace will have its own portal customizations,
managed docs, content sources and index settings. So if you want the
portal to be customized for a particular group  or division, you would
have a dedicated workspace. Users may have permissions to multiple
workspaces.

A dashboard is a part of the portal, each top-level tab is a dashboard.
A dashboard contains web parts or other dashboards  (sub dashboards). SPS
ships with some basic dashboards like home and Search. You can add
dashboards and to them you might want to add sub dashboards and ofcourse
web parts.

Depending on your requirements you probably have 2 ways to go.
First a single  workspace with a portal that everyone can use and agree
on.
Next multiple  workspaces, each with a specific portal for the groups
needs. You can then apply permissions for users in each of the portals
if need be. You can also have each portal index the other portal and
each user  would generally stay in one portal and has search capibilites
arcoss multiple portals.

Thanks for this very informative explanation. I just realized that since
I am looking at the v2 beta, the idea of workspaces  and dashboards  has
completely changed.

I guess I picked the worst time to try implementing an MS portal
solution. Version 1 is on the way out. There is little documented
information about configuring and using Version 2. And, worst of all,
Version 2 looks to be almost an entirely different application than
Version 1.

Unfortunately, we don't have the luxury of waiting 6 months before we
implement a solution.

Wish me luck. I'm going to need it.

You are indeed in the middle. Keep an eye on this list as well as
others as these are the places where V2 will be discussed. Good luck and
keep asking question and answering them here so we all can learn!