I think you would have to have some sort of event handler that fired after a
certain timeframe that emailed the documents added today.
Is there a reason why you wouldn't just add an alert and let the user log in
to see the daily  documents added? If its due to external partners, you can
still create a log in for them and even create a separate library for daily
documents added.

I am interested in Liz's question but for a slightly different reason.
I would also like to set up some kind of daily  agent that triggered an
alert, just as a way of checking the alerts are working (i.e no email
in the morning, alarm bells ring). Equally, we occasionally find that
WSS search stops working, it is easy to fix (rebuild the SQL full-text
catalogs in our case) but if there was an automated test each day that
would be really helpful.

Do any admins out there have any 'widgets' that they find helpful for
tests such as this? I suspect that what Eric said is right and the
only way to do it is event handlers and triggers and .net code but I
don't have those skills (although one day hopefully).

I believe alerts will work just fine in some cases, but
for this instance, I believe I would need to look at having an event
handler do the job. I will get my programmers to take a look.

In v2, you will need to write a custom program that the OS will run
every day. An event handler doesn't have a time element, just events.

In v3, you could write a SharePoint Timer Job. An event receiver or even
a workflow doesn't have a time element, just events.