Fallout: New Vegas Unlockables

Fallout: New Vegas Companion List & Location
Here's a list of the unlockable characters and where they can be found.
UnlockableHow to unlock
Craig BooneFound in Novac. Complete the "One For My Baby" quest you receive from him. Note; keep a respectable karma level with NCR or he will not speak with you.
RexLocated at The Kings in Freeside. Complete "Ain't Nothin' But a Hound Dog" to receive Rex.
CassLocated in Mojave Outpost Barracks sitting at the bar. Complete the sidequest "Heartache by the Number" to receive Cass as a companion, which will give you an additional quest "You Can Depend on Me".
ED-ELocated in Primm. Repair him and receive "ED-E My Love".
Arcade Israel GannonLocated in Old Mormon Fort inside Freeside. You can only recruit him if you have a bad reputation with Caesar's Legion.
LilyLocated in Jacobstown (west). Complete the sidequest "Guess Who I Saw Today".
Raul TejadaLocated inside the prison of Black Mountain. Access the prison terminal, and complete "Old School Ghoul".
VeronicaLocated at the 188 Trading Post, north of El Dorado Dry Lake. Speak with her in good light about the Brotherhood of Steel and she's all yours.