searchnuggets

It may pay off to follow a systematic approach for constructing queries when you're googling a topic, or engage in other kinds of online research. You never know what you are NOT finding, and query reformulation is often done quite haphazardly. The Search Matrix is a technique used by librarians, helping you define wider and narrower terms, synonyms and acronyms for topics you are researching.

Faceted search is a technique for accessing a collection of information represented using a faceted classification scheme.

In a faceted classification scheme, each object or document can be classified based on multiple facets that represent independent ways of describing it. For example, the facets in a product catalog include category, brand, price, etc. The facets in a library catalog include subject, author, time period, etc. Faceted classification represents the fact that, as David Weinberger says, Everything is Miscellaneous, and it is artificial (if not impossible!) to arrange a large, diverse collection into single, pre-determined, hierarchy or taxonomy.

Something a little different, Soovle shows query completion for several search engines at once, and lets you easily flip from engine to engine. The search itself, once you hit the "Soovle" button, is executed only on the engine you selected.