A collegue of mine logged a wish at the Office 2007 beta program about the aggregation of RSS feeds in SPS 2007. Below the wish and the respons of Microsoft:
"Given Sharepoint3's widespread adoption of RSS syndication, why is there no *built-in* Sharepoint RSS aggregation webpart?
I realise that both Outlook-12 and IE-7 have aggregation support, but neither is a good substitute for a strong internal Sharepoint facility.
I realise also that there are a number of 3rd-party Sharepoint RSS aggregation web parts available, (and these are also not too difficult to write in house) but I'd prefer native S'point support (i.e. an aggregator web part).
Also, will shipping S/point3 make it easier to find RSS feeds? Seems unnecessarily messy right now.
I'd prefer native SharePoint support for a facility (i.e a web part) that would, for example, allow aggregation on, say, the Home Page of the portal. The web part could aggregate all postings with a Weblog Category of "HomePage"."
"This issue has been fixed in a newer build of Office 12. The Product team says there is a web part for anonymous RSS feeds - it's called the RSS Viewer Web part. It is part of Beta 2."
So it looks like there will be RSS aggregation support in the new release of Sharepoint.