What apps do you use to organize and plan daily activities?

[L R Wadsworth]

As a superintendent for a production and semi custom builder I'm expected to be as organized as possible. I'm very much old school when it comes to calandars and home specs in paper form. I'm curious to know if there are any specific apps for the iPad or iPhone that is being used in scheduling start dates, target finish dates, sub management, homeowner appts, etc... I see the need to be more modern with my organizational skills, but will always have the good ol trusty pen and paper handy!