[Air-L] Studies regarding users/use of Twitter or

Hi! I am a very late adopter to Twitter - or so it seems to me. To really understand Twitter, I would love to get my hands on any data concerning it - I of course tried to search and ask on Twitter itself, but... So any kind of link or information regarding Twitter users, useage, by socio-demographics or whatever, would be very much appreciated. I am a quiet reader from time to time, BTW...for long :-) Have a great day/evening/night! sam