After years of trying to figure out how to keep track of an ever-growing array of events and to-dos, my wife and I finally settled on iCal, Apple's calendaring program. iCal syncs seamlessly with my Zimbra (work) calendar, and easily syncs with my wife's iPhone, where she inputs most of her appointment data.
The result? Pure bliss. No more, "But you didn't tell me you'd be out of town on that day!" Gone are the days of (blame-free) accusations like, "Why did you schedule soccer practice right in the middle of Greta's parent/teacher conference?"
Now we get to argue over more substantial things. Like whether Arsenal has a chance of winning the Premiership this season. :-)
If you've never used iCal, it's fantastic. I just had to publish my wife's calendar on her computer and then subscribe to it on mine. I used Zimbra's CalDav sync functionality to let her subscribe to mine. Seconds after I change my calendar, she knows. She's orange; I'm blue. Easy.
The Asays, back together again. At last.