Japan has seemingly jumped into the future -- as people are going to concerts of a Computer Generated Singer/Hologram! Hatsune Miku, a blue haired anime girl is actually a computer generated singing program called Vocaloid. Her Avatar, though, was able to be projected onto a concert stage using an updated version of an old method, something called Pepper's Ghost Illusion. Even from a youtube video, it looks like a pretty darn good illusion. You can see concert goers on either side of the stage, with Miku moving in-between them - so it wasn't something just projected onto a screen.
Miku has apparently been rising in popularity in Japan with a cult following. The Vocaloid Technology isn't exactly catching on over here in the US, but maybe exposure like this might peek some company's interest.
It looks like a really fun experience for concert goers - and you can see the song on this video here. It's actually very good and catchy. Not bad for a piece of software.