A great site for teaching how to use boolean logic when searching the web.  Students/Teachers start by searching the web, news or images (the search is powered by Google).   Using a search screen similar to a puzzle you then type in a keyword and results are shown.   Users then refine their search by adding pieces that represent AND, OR and NOT and another keyword.   The resulting number of hits on the search are immediately shown.   The site helps students understand their web search by visually showing the logic of their search.