Update 2009-08-22: Two new(ish) changes to report! The first is that with the release of iPhone OS 3.0, it is now possible to subscribe to Internet calendars directly from the device. The second is that NuevaSync now offers a premium service which includes push e-mail and up to 50 calendars. I’ve updated my post accordingly.
Update 2009-02-26: I’ve added the steps to set up synchronization using Google Sync to the post.
Update 2009-02-14: Google now provides wireless synchronization capability directly. The instructions for setting it up are here.
I’ve been using a great free service called NuevaSync to wirelessly synchronize my Google calendar and contacts with my iPhone. It’s essentially a proxy to Google’s contacts and calendar services that allows you to synchronize them with any device that supports the Microsoft ActiveSync protocol, including the iPhone and Windows Mobile devices.
When the service first launched, you could only synchronize with Google calendars which you had read/write access to. Recently, however, they have enabled syncing with read-only calendars. This includes services which publish an iCal feed which you have subscribed to in Google Calendar. And since Facebook Events provides an iCal feed, you can subscribe to it in Google Calendar and have the events show up in your iPhone calendar.