One thing that I wanted to do (but didn't) was take a photo of myself and my husband and write your daughter a birthday letter. Then put it away for safekeeping.
Another thing that I DID do was on the advice of a friend, my husband and I started a journal that we will give to our daughter when she grows up. We write down what she has been doing, saying, milestones, and other funny things that (as a parent) you tend to forget even 3 or 4 months down the road. We write our hopes for her in it, or things that are going on in the world, anything that might give her insight later as an adult as to parenting. I'm sure by then we'll be senile haha, but no one can remember those sweet details 20 or 30 years down the road.
We also make photo albums for her of her life, include pictures of friends, pets, places, and she has been looking at them since she was barely old enough to sit up. She loves her albums, and helps her identify her family that is far away, and special places.
Good luck!