Feed Digest. There are a bunch of RSS feed engines out there, which let you embed feeds on your web site with minimal fuss. But this one really looks polished and full featured, if you know what I mean? Not only does it do the feed thang, but also turns RSS into Javascript includes or WAP pages for mobile phones and lets you syndicate your own content for other sites. It was built using Ruby on Rails and currently handles around 200 million requests per day, which says something about the robustness of the Rails framework. Definitely worth checking out.