I didn't send out birth announcements for any of my three kids. I think it comes from the same part of me that doesn't send out Christmas cards. When we were in Arizona an surrounded by family that was all at the hospital when the baby was born, it seemed silly to send them an announcement.
But if I had sent out announcements I would have wanted them to be something like these glassine birth announcements that Meredith from Lily Jane made:
Cute, small, and practical. Now that we live away from family I am trying to be better about sending cards. I am still working on it, but I think this idea would make a really cute valentine for Grandparents. You could type a message on the glassine bag and slip in a cute picture of the grandkids. Then they could keep the picture toss the bag after Valentine's Day.