Windows/Mac/Unix (Firefox): Firefox extension Tab Groups lets you organize your Firefox tabs into - you guessed it - more tabs! Just create and name your high level tab groups, then organize your existing tabs into new groups or move them between groups with a simple drag and drop. Tab Groups is a very new extension (still in alpha, in fact), but the core functionality is already there and so far
![Tab Groups (Firefox) - Lifehacker](https://cdn-ak-scissors.b.st-hatena.com/image/square/7a71f2e2553f44c11cee2ed0c654fc979ad00fb0/height=288;version=1;width=512/https%3A%2F%2Flifehacker.com%2Fimagery%2Fdefaults%2Ffallback-thumbnail.fill.size_1200x675.png)