Even though iPhone 3.0 supports CalDAV, there still doesn't appear to be an easy way to get the "Birthdays" calendar to sync to iPhone over MobileMe. Enter Dates to iCal, by John Maisey, a background script that creates and maintains a new calendar in iCal containing all of your birthdays and anniversaries. Because iCal sees the new calendar as a standard calendar, it syncs effortlessly using MobileMe. Within 60 seconds of turning on Dates to iCal, I could see all of my contacts' birthdays on my iPhone and on my two Macs running iCal. I then published the new Birthdays calendar to Google using BusySync, and my Blackberry Bold now also sees the calendar after syncing with Google Sync.
General notes on syncing Macs to Google to iPhone to Blackberry: I have been a loyal user of BusySync for some time now; it allows me to sync my iCal calendars to and from Google.
My calendar sync looks something like this:
> iPhone <-MobileMe-> Mac <-BusySync-> Google Calendar <-Google Sync-> Blackberry
Even I'm amazed that it works.
iPhone's new CalDAV support means that I could probably start hosting my calendars in Google and subscribing to them via CalDAV in iCal and on the iPhone, but it's all working well right now and I don't have the energy to re-think things, especially when it all seems to work.