The ability to edit Google Calendar on iPhones is now possible. The new version is best used through a shortcut on the homepage.
The new Google Calendar for mobile supports iPhone OS 2.2.1 and up and all Android-powered phones. It’s available in English only for now, but more languages will be supported soon. For Apps users please go to google.com/m/a/yourdomain and click on Calendar.
The new version allows users to respond to event invitations, send event invitations, change attendance status, as well as edit events directly from the phone. The previous version was view-only. The new version will also show the most recently viewed event if no wireless network is available.
[via Google Mobile Blog]