NOTE: Not in active development.
This extension allows users to perform searches or look-ups in arbitrary engines without leaving the page. Searches are performed by holding a key and double-clicking a word, or selecting it. A small inline box pops up with the results. The extension works for any search engine or online dictionary, and allows users to specify their own choices.
A little useful feature is the ability to specify default scrolling actions for each source, so when a search is performed, the pop-up will automatically scroll to the appropriate section of the page.