Sync Calendar Between 2 iPhones

I searched for my question, but was not able to locate anything. I apologize if this has been asked before.

My wife and I both have iPhones. She doesn't spend much time in front of the PC and her phone doesn't get synced very often. Is there a way we can "send" calendar entries to one another?

I say "send" as I know that I can't literally forward a calendar entry (which would be ideal), but I am willing to use something like .Mac if that'll help at all.

In a perfect world, I'd like calendar entries she makes to find their way to my phone without requiring her to sync. Can she sync her iPhone calendar with .Mac over the air (if that makes sense)?

Thank you all for your time.

Paul