Google Calendar?

Anyone use Google Calendar? I just set it up but I'm getting the feeling that there is a lot more to it than what I've done with it. I've created separate, color-coded entries for my appointments and the kids' appointments. I like that everyones' birthdays will repeat as a yearly event and I won't have to re-input them at the beginning of the year. I don't have an iPhone, but I see that I can have it sync to that if I did. What other cool things can I do with it?