A bunch of folks at work have been prototyping a server-side RSS reader at http://www.start.com/1/. This isn't a final product but instead is intended to show people some of the ideas we at MSN are exploring around providing a rich experience around Web-based RSS/Atom aggregation.  

The Read/Write Web blog has a post entitled Microsoft's Web-based RSS Aggregator? which has a number of screenshots showing the functionality of the site. The site has been around for a few weeks and I'm pretty surprised it took this long to get widespread attention.

We definitely would love to get feedback from folks about the site. I'm personally interested in where people would like to see this sort of functionality integrated into the existing MSN family of sites and products, if at all.

PS: You may also want to check out http://www.start.com/2/ to test drive a prototype of a Web-based bookmarks manager.