Starting teams features Reikland Reavers (humans from the Empire), The Gouged Eye (Orcs) and Skavenblight Scramblers (Skaven). See more about team details from the official site.
There is also Blood Bowl Death Zone: Season 1 gaming supplement. This book will feature details about 7 new teams (including those Skaven mentioned) and many other interesting rules to expand the game.
See more info from official site Blood Bowl - The Game of Fantasy Football
and from the Games Workshop Shop: Blood Bowl & Death Zone: Season 1.