Chrome: Twitch.tv, the streaming service for gamers, has been growing in popularity over the last couple of years. Twitch Now allows you to manage all your subscriptions and streams from one easy button.
The extension lives in your extensions bar (as they do). Click the purple button and you can pull up a list of your favourite streams, search for a specific channel, or browse currently active streams by game or what's popular at the moment. You can even get a notification when one of the streams you follow becomes active.