Trufflepiggy - Quick Search - The all-in-one search addon: just select and search. Find on multiple websites at once. Search via overlay, context menu or omnibar. Featuring anonymous profiles. Easy setup: select from 1000+ user generated searches. Cross-browser sync.

Swift Selection Search - Swiftly access your search engines in a popup panel when you select text in a webpage.

Context Search - Context Search is a Firefox extension that expands the context menu's 'Search for' item...

SearchJumper - Assist with the seamless transition between any search engine, providing the ability to swiftly navigate to any platform and conduct searches effortlessly. it allows for the selection of text, images, or links to be searched on any search engine.

Selection Search - With this extension you can easily search for text you have selected.

SearchWP - Instantly improve the search experience of your WordPress site today with SearchWP, the best WordPress search plugin you can find!