What you may not know is that you don't need the new Galaxy S3 in order to do it. Visiting any website in OverSkreen, a web browser from developer MBFG, is just the same as visiting it in your normal browser until you realise that you can shrink the window from full screen to something smaller and it doesn't disappear from sight when you launch an app.
Yes, that's right, it floats on top of your screen meaning you can do two things at the same time on your phone or tablet. And yes, it works just fine with video sites such as YouTube. Available from the Play Store (or Android Market to those who still think the new name a little daft) for less than it costs for a decent cup of coffee the browser offers you the best of both worlds, a decent web browser but with the benefit of true multitasking thanks to its unique ability to float.
MBFG have cornered the market when it comes to floating windows, with a number of floating window apps that include a terminal and a dedicated video player this is one developer that manages to make Androids multi tasking nature even more useful. iPhone users will perhaps be disappointed to find the app is only available for Android devices but if you have an iPad and it's jailbroken (and running at least iOS 5.0) check out Quasar which is a tweak (not from the same developer) that lets you open multiple apps in multiple windows but be aware it does cost a lot more at just over six pounds.