I was contacted recently by Pavel Kounitsky the developer of Quisple and I really think its's a cool little app, can't wait to see how it progresses. Quisple streams music from YouTube and even builds play lists. Have you ever been thinking of a song and just want to quickly play it without the hassle of opening the browser and searching YouTube or some other site? Quisple is the answer. It's a Windows only application, but I got it working in Wine on OS X 10.6 using Winebottler so I'm sure it will work in Linux also. All you really need is Firefox and Flash installed in Wine for it to work. 

Here some pics, the settings I used are in the first image, click for bigger. Once it completes you will have a, whatever you named it. .app on your desktop ready to run. Requires x11...

One more if you care to see it running... Click Read more ;)