There are only two branches of military within the alliance, which is the Naval Branch and the Marines branch. Within both branches there are different things you can take.
Marines
Marines
Vanguards
Armored
Naval
Navy
Both Marines and Naval
The Angels (Requires good combat record, and lots of experience)
Ships of the Alliance (listing names of ships for now and maybe class)
ANS Pegasus-Crusader Class Dreadnought
ANS Devastation-Crusader Class Dreadnought
ANS Phoenix
ANS Galaxy's End
ANS Battlestar Eternity-Battlestar Class
ANS Battlestar Constitution-Battlestar Class
ANS Silver Cloud - Cruiser Class Survey Ship
ANS Aoen-Crusader Class Dreadnought
ANS Battlestar Centurion-Battlestar Class
ANS Warhawk
ANS Archon
ANS Drake
ANS Dragoon
ANS Dragon
ANS Storm
ANS Hurricane
ANS Rising Star-Crusader Class Dreadnought