just wondered what kind of the things some of you guys use to achieve Arduino controlled locking?
I would go with either a solenoid or servo operated arrangement. A lot depends on on the specific locking mechanics you are having to deal with. The ones I've dealt with are solenoid operated strike plates where the controlling mechanics and electronics only have to mount on the fixed frame of the door, rather then on the door itself.
Don't forget to design for a default unlocked mode in total power failure as human safety can be at risk.
Good luck
Lefty