iOS: Agenda is a calendar app that prides itself on its minimal appeal, but don't be fooled: the app gives you quick access to your appointments and important dates all in one view.
The app allows you to swipe back and forth between day, week and month views, and see your schedule appointments for the day or the week. You can bring up appointments, tap to call contacts or tap addresses to get directions, and even browse multiple weeks or months all without bringing up the keyboard once.
Agenda is designed to remind you of events and get you to them quickly. It doesn't do well when it comes to adding appointments, but it does sync with iCal, and you can sync iCal with other calendar services to keep Agenda up to date. It'll set you back $1.99 in the iTunes App Store.