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Diigo Research Tool Diigo does a very good job of searching tags across several sources and presenting results, and can also serve as a collaborative research tool. On a search for classification it picked up results from del.icio.us, Yahoo MyWeb, Bloglines, Technorati, and Digg - a mix of social bookmarks and blog postings. Google links comes into play when you inquire on a specific article - but the Google backwards link search is known for being incomplete and weak. This information is displayed on the About page for each result along with tags, bookmarking names, postings, and comments -- all in all a very informative page.

But Diigo is more than a metasearcher. It's a collaborative research tool. You can form groups here, and add your bookmarks to Diigo and other services you use. In addition you can clip pages and add stick-notes.