Heard of the Arctic Monkeys?
 

just broken all album sales records in the UK. 100,000 albums sold in one day. over 360,000 sold in first week

and all promoted virally and through word of mouth. they gave away cd's/mp3's of their songs and were happy for them to be passed on. the quality of the music sold itself and they don't even give any interviews

instant millionaires and they all still live at home with their parents

Yep, known them for months :)