They are taking submissions now!! For anyone interested in going I suggest you make your hotel reservations now as most of the rooms downtown are already booked. If you end up staying outside of downtown the taxi fares are killers!! Anyway here is the link for info on submitting your group
http://2008.sxsw.com/music/festival/apply_to_showcase/
http://2008.sxsw.com/music/festival/apply_to_showcase/