I first came across the FullCalendar jQuery plugin while searching for a better way to mimic the features and style of Google Calendar. I was immediately impressed; it combined features like drag-and-drop and dynamic resizing with the limitless flexibility of an open-source project.
Whenever I come across a new technology or service, the first thing I do is check to see if there is a Drupal module available. As is generally the case, there already was a Drupal module released, though only as a beta. Only the most basic features had been implemented, so I dove headfirst into the issue queue, submitting feature requests and filing patches. After several weeks of enthusiastic back-and-forth, the maintainer decided to turn the project over to me, and focus on his freelance work.
While at Zivtech, the FullCalendar module has flourished, with the addition of real-time drag-and-drop, event resizing, and translations. The module now has stable releases for both Drupal 6 and Drupal 7, and work has begun on the next major release for each version of Drupal. Yet to come are features like improved accessibility, integration with public Google Calendar feeds, and fully customizable event color-coding. The standard Calendar module has long been a source of frustration for users of Drupal, and is not yet available for Drupal 7. Adoption of FullCalendar has risen steadily with the release of Drupal 7, as the ease and simplicity of FullCalendar makes it a welcome addition to any site. See a demonstration: