Earcandy is the next cool thing you want in Linux
Earcandy is a PulseAudio volume manager, which for me is probably the first thing that i ever liked about pulse audio. This volume manager could mute music in your amarok or rhythombox or literally any music player when you play some video in youtube or VLC or other video players.
Mute is not the right word, but instead the music slowly fades away, and the sound from video player fades in. Sounds promising eh? But it is much better than you think.
* Smart Volume Detection:
When a video player is swithched on, music from your music player slowly fades out(of course you can adjust the 'slowness' anytime). But what happens when the video is stopped or paused. Yeah, you guessed it right, the music player starts playing again! Delightful isn't it? This includes the youtube videos in your browser as well. blah!