A handy add-on for Firefox that saves us from scrolling through all the open tabs in search of the new one we’ve just opened. (That came out as a tricky sentence :)
New tabs open immediately to the right of the current one, so we group them by topic without thinking about it. (That’s clearer, I think.)
A tip for beginners: it’s very convenient to open new tabs with a click of the mouse wheel (they also land to the right of the current one) or with Ctrl+T (T for “tab”).