Chrome: Using YouTube for music is brilliant because it's free, has close to every song out there, and works everywhere. The problem is that it's easy to accidentally close a tab in YouTube and it's not easy to queue up songs without creating an account. Streamus is an extension for Chrome that makes that all easy.
With Streamus, you can type Streamus: "song you want" into Chrome's URL bar and it will instantly start playing the song from YouTube. You can also add new songs to a playlist, or create a radio station based on an artist. It's a simple idea, but it allows you to enjoy all that music on YouTube without keeping a tab open all day long.