As noted by PhotoMatt Googlebot has been randomly requesting atom.xml, index.rdf and rss.xml from many webservers in the last few months.
Not only does this suggest that Google is actively indexing RSS news feeds because it values them as a good source of information but also that people who publish RSS news feeds should name their feed file :
Either index.rdf or rss.xml – for an RSS 0.92, 1.0 ,or 2.0 feed
atom.xml – for an Atom RSS news feed
To increase the chance of Google and other search engines indexing their feed.