Apple's built-in Calendar app for iPhone is fine, but I prefer Fantastical, a $5 alternative from Flexibits. Because the app can access your iPhone's calendars, it essentially offers complete integration with any calendaring system your iPhone can use or sync with--including iCloud, Google, Yahoo, and Exchange calendars. I reviewed the app in November of last year, awarding it four mice.
In the video above, I offer up a quick tour of Fantastical's core features. It features a scrolling list of upcoming appointments, instead of a more traditional grid approach. The app allows you to create appointments using natural language, and handles the scheduling automatically. And it offers fast built-in search, too.
Fantastical for iPhone requires iOS 5 or later.