HTML 5 isn't officially finished yet however that hasn't stopped developers using the code. It's been used all over the internet now and most modern websites use the coding language. HTML 5 is also a lot more versatile than previous languages and can allow cool animations and features which would only usually be possible with Flash. It's used by nearly every single modern browser like Chrome and Firefox and Android and iOS devices support it too.
Here are some great websites using HTML 5: