When the iPhone first came out, the functionality of the Calendar app was limited. You could track your calendar on the iPhone, but, since the iPhone couldn’t sync with an Exchange calendar at the time and, even if it could, Google wouldn’t release Google Exchange Sync for two more years, you could not sync your iPhone calendars over the air. Your only option was to plug your iPhone into your PC and sync with a desktop application like Outlook. Much has changed since then. Now you can not only sync your calendar wirelessly, you can do so with multiple calendars, whether they are with your work’s Exchange calendar, with MobileMe (now iCloud), or with Google. Still, there’s some room for improvement. For example, you can only look at your calendar in Portrait mode, not Landscape (this may change in iOS5). You also only have three calendar views in the default app. Fortunately, there are many iOS apps out there which can turn you calendar into the full fledged powerhouse that you need to keep organized. I’ve reviewed three of the best, although, in my opinion, one stands out above the others.