I suspect our most recent requirement will involve custom web parts
that provide a "dashboard" that reflects the status of documents in
a number of document libraries.

As best I've heard it explained, it goes like this:

There's a thousand "reporter" users that can "create" a document in
any number of document libraries. There's a dozen "reviewer" users
that need a "red light" to come on when such a document is created.

They need to be able to click on the red light to open the document.

When they close the document, the red light goes dim.

Since each of the dozen "reviewers" will review these documents
asychronously, therefore, at any given time, each reviewer will see
a unique combination of of red lights\dim lights, each one lighting
up to indicate that there's a document that that particular reviewer
has yet to review.

For example, you and I are reviewers and say there's doc1, doc2 and
doc3, each a doc library.

And say one document is created, new, in each of the three doc
libraries.

I look at the web part and I see three red lights
labeled "Doc1", "Doc2" and "Doc3" respectively.

I click on "Doc1" and the new document in the Doc1 library opens.

I close it and the "Doc1" light is dimmed but the other two are
still red.

If you were to look at the web part, you would still see all three
lights red.

Solution:

I'm not great at this but my best guess is that I need a database
tables that store:

Table 1: The reviewer names

Table 2: The Doc Library name and GUID of each document paired with
each reviewer name and a status of Red or Dim.

Then, when the web part opens, for each light, I have to query table
2 for the doc library and current user, check for "status = Red"
and, if I find one, point the graphic object to the red light and
link it to the GUID.

Then when the doc opens, update the table setting status to "dim"
for that GUID\Reviewer combination.

How that sound? Is there something like and XML trick or a web
service I could write to make this work without the database part?