According to the unofficial Google weblog, MSN search users can now enter the following operators into the MSN search engine as follows:
feed: The feed operator returns feeds matching the search query. The results are raw feeds; click on one and you get .xml code. However, click on the “Cached page” link to see an intelligible feed display as you would in a newsreader. MSN crawls full feed content.
hasfeed: this operator returns matched results of Web pages that include a link to a feed. By and large, the linked feed is the feed for that page or site, not another, so hasfeed: offers a secondary and more familiar, Web-centric method of finding content.
RSS and Atom feeds come from other sources besides blogs so this wouldn’t necessarily act as a blog specific search engine but it does come pretty close. This could come in as a handy tool for users who want to search for relevant content for syndication on their sites or for reprint purposes.