Catalyst Game Labs have released the BattleTech Starter: Fist and Falcon and two other PDF supplements.
From their announcement:
BattleTech Starter: Fist and Falcon brings players a new and exciting way to jump into the BattleTech universe. As conflict erupts anew on the Lyran-Falcon border during the early years of the Jihad, two untested commands clash. Including the brief history and personal dossiers of the members of these two forces, this PDF provides scenarios and special rules compatible with BattleTech games using Total Warfare and A Time of War, complete with record sheets for their ’Mechs and characters alike.