My favorite meta-search tool Vivisimo was PC Magazine's Site of the Week last week, and it gets a pretty good review. Although Vivisimo has a ton of great features, my favorite (and its claim to fame) is its clustering engine, which groups your results into topic-based folders. This is a terrific way to narrow your search focus. Vivisimo recently released Version 4.0 of its clustering engine, which makes several improvements over the previous version.
For those of you who haven't tried Vivisimo yet, what are you waiting for? You'll be pleasantly surprised at the results.