I had a hand in developing the workflow Gerald desribed, and I have pasted below a screenshot of the workflow design.
Essentially, the workflow called the search webservice (twice) with a CAML query to return all the news and calendar items that had been created on the site within the required date range (in this case it was a week). An XML query was also used to query some custom XML, which returned the events within the site, which were going to occur in the coming week.
All of the results of the XML and webservices calls were formatted using XSLT and stored within workflow variables, before being added to the notification email and distributed to subscribers.
One of the benefits of using XSLT, was that it allowed us to format the content and present imagery within an email notification (functionality not native to workflow), by placing an image on the intranet and referencing it's URL.
Unfortunately I dont have any newsletters i can show you, though i'm happy to answer any questions about it.