Microsoft had some special RSS search operators in Live Search to help users search across RSS feeds or discover blogs on particular topics.

RSS Search Operators

To find blogs and feeds about iPhone, type feed:iphone in the search box. Similarly, to find blogs that are about Global Warming, type feed:global warming - the search results directly point to the XML feeds and automatically sorted by relevance.

Another RSS search operator is hasfeed: and as the name suggests, it finds web pages that contain an RSS feeds for the keywords you search for.

For instance, to find all google related blogs hosted on blogspot.com, you can type hasfeed:google site:blogspot.com. Another example could be site:nytimes.com hasfeed:david pogue that show all webpages from New York Times website which have an RSS feed related to David Pogue.

Microsoft Blog Search Engine

The Live Search also has a blog search feature much like Google Blog Search or Technorati though it is very limited in features and indexes relatively lesser number of blogs. To access Live Search Feeds, go to http://search.live.com and click Feeds.

The feed: and hasfeed: RSS search operator won't work with Live Search Feeds.