qts, Quick Torrent Search

A Firefox add-on that enables you to search for torrents directly from
the context menu. Simply select some text, right click, and search for
torrents on your favorite site.

https://addons.mozilla.org/en-US/firefox/addon/quick-torrent-search

Note that the Chrome version was removed from the web-store as it
violated their terms of service. If you would like to still use it
you can install it from source here (qts/chrome).