I don't normally recommend expensive app downloads for your smartphone or otherwise, but I'm making an exception for Fantastical ($15). Yes, you read that right, the app is $15, but in my world, this app is magic.
Fantastical is a "natural language event creator" that allows you to type out event details as you would say them, then the app automatically populates your calendar details. Working seamlessly with iCal, Entourage, or Outlook, you can create events, color code them, add alarms and reminders, and quickly be on your way. Best part, your calendars don't even have to be running since Fantastical syncs on its own. If you live and die by your calendar events and reminders like I do, this is the app you want to splurge on. It's saved me so much time!