SimulTwitch

SimulTwitch is a very user friendly way to watch multiple Twitch streams at the same time.

It enables you to watch unlimited streams (assuming your computer can handle it) at the same time, allows you to save your own favourites and includes easy ways to re-order and manage the streams you're watching and the favourites you have. You can also easily create a shareable link that you can send to friends so they can watch the same group of streams as you, or you can just copy the URL from the browsers address bar.