This page currently only lists the main blog search engines with descriptions provided by the services. This is currently a very hot area and more info/reviews (and search engines!) will be coming shortly. If you are looking for more detailed information about how these search engines work and how they compare with each other, Mary Hodder of Napsterization has compiled a comparison PDF chart of blog search engines.
Technorati is a real-time search engine that keeps track of what is going on in the blogosphere — the world of weblogs. Technorati displays what's important in the blogosphere — which bloggers are commanding attention, what ideas are rising in prominence, and the speed at which these conversations are taking place. Technorati makes it possible for you to find out what people on the Internet are saying about you, your company, your products, your competitors, your politics, or other areas of interest — all in real-time. All this activity is monitored and indexed within minutes of posting. Technorati provides a live view of the global conversation of the web.
PubSub matches your requests against new information as it appears in real time, all the time. Traditional search stores data and then allows you to find documents within that store of data. PubSub operates by first storing your subscription query, and then watching for new information that matches it. Your query will be checked against every piece of new information passing through our Matching Engine.
Bloglines provides blog search apart from its regular feed reading capabilities.
Blogdigger uses state of the art syndication technologies, such as RSS and Atom, to index blog content and make it available for search. Blogdigger also makes all search results available in RSS or Atom, so users can subscribe to keyword searches and automatically be notified, via the News Aggregator of their choice, of new content pertaining to their interests. Blogdigger searches thousands of RSS and Atom feeds, and is built-in to many popular News Aggregators, such as FeedDemon and NetNewsWire.
BlogPulse is a window into the blogosphere. Open it daily to discover the people, issues, blogs, posts, commentaries, tidbits and news that bloggers are discussing. Features trend searches.
RSS Network - Easily find topic specific RSS feeds by searching or navigating RSS Network's directory.