My baby journal.
I write in a 5 year long, one comment a day journal. I started it when Imogen was a couple months old... I jot down what we did, how I feel, or random little thoughts I have about our day, our family, her, motherhood, life, etc. I write in it as if I'm talking to her, and someday it'll be hers.
I used to track Imogen's nursing schedule but only for a couple months when we had some weight concerns and had to suppliment, pump, wake her to nurse, etc... I'm SO glad we're through that! When I don't *need* to, I slip up on tracking things. But I can handle one random line a day of 'mommy thoughts'. ;)