Creating Site Roll-ups in Sharepoint with RSS
Roll-ups of information from several (top-level or nested) Windows Sharepoint Services sites has been a “nice-to-have” feature mentioned in several Sharepoint projects I've been involved with. Commercial solutions is available in the market, like the CorasWorks package. However these solutions tend to be too expensive to justify.
By using a combination of RSS feed generation and RSS feed consumption webparts (both opensource or freeware) it is possible to create roll-up like functionality with minor configuration effort.
The Leadit.Sharepoint.Services, written by Jan Tielens, provides an RSS feed for every site in the portal, and the SmilingGoat FeedReader displays such feeds in a webpart. (More Sharepoint RSS solutions listed by Daniel here).
By configuring the FeedReader as illustrated we can extract information about changes in all or selected Sharepoint lists on a certain site. The FeedReader of course allows us to configure several feeds for display thus creating a nice rollup of for example all Issues lists or Announcements lists.
Some minor features are missing to make this a really powerful setup. Jans "What's New" service should be able to use list inclusion instead of exclusion, and probably you'd be more flexible using multiple intances of George Tsiokos DataView RSS solution for display.
All in all this is a couple of hours of configuration at max makes for a pretty cost-efficient roll-up solution which also gives users the possibility to aggregate Sharepoint content in their favorite RSS reader.