Donna entered the App Store in the spring of last year. Since then, the app that lets you manage your day has added many new features, fixed a few bugs along the way and done a nice re-design for iOS 7. It's also now free.
Donna can tell you when to leave for a meeting, can dial into conference calls, give you the weather outlook for upcoming appointments and let people know if you are running late. It knows when you are on the way without having to input that information, and it provides daily summaries and summaries in the evening for your activities the next day.
With all that power, Donna is easy to operate. You do need to sign up for a free account. Favorite locations can be saved, and it syncs with your calendars including Exchange, Google, Apple's iCal and Yahoo. The app can provide driving or transit and walking directions, and using Google Street View, it will show you your destination.