If search engines have an Achilles heel, it's that the crawling process lags the content creation process. While content from some sites appears quickly in search engines, it takes up to a month for crawlers to do a comprehensive refresh of all new web content. This means that all search engines, no matter how comprehensive, are to one degree or another out of date.
Today's SearchDay article, Managing the Firehose of Real-Time Information, focuses on PubSub, a service that monitors blogs, SEC filings, Newsgroup postings and other sources, and matches your keyword based queries against those sources in real-time. It's a great "prospective" tool for supplementing the "retrospective" results you get with search engines. It's also a terrific early warning system for new sources of information that you might miss using other tools, such as feed aggregators or blog search engines. Definitely worth a look.