OggSync 2.0 FreeWare offers complete two-way syncing between your phone and your Google calendar, including support for repeating events and modifications to those events. It enables over-the-air or cradled connections to ensure you're always updated.

However, OggSync 2.0 Freeware takes things up a notch. Not only does it offer full 2-way syncing from your phone to one of your Google Calendars, it also supports Google Hosted Domains. Plus, you get complete support for repeating events and changes to those repeating events. With OTA or cradled connections, you'll always be up to date. And, it's compatible with Outlook and ActiveSync. Plus, you'll be notified and able to automatically download new versions when they're available.
For even more robust features, there's OggSync 2.0 Pro. With this version, you'll be able to sync multiple calendars, both public and private, automatically. The default calendar mapping feature allows you to map events with no matching Google Calendar category to your default Google Calendar. Plus, existing subscribers get an automatic full upgrade to the Pro version.
OggSync's mission is to keep mobile users in sync with the scheduling demands of a busy lifestyle. Whether you're using Google or Outlook, OggSync helps keep all calendars in one manageable view. With OggSync Basic, you can keep your one calendar synchronized to your Windows mobile phone for free. And for those who need more, OggSync Professional allows users to synchronize multiple calendars to their mobile phone and provide for automatic updates.
Version 2.15 GA: - more reliable syncing.