The Geekdad blog today suggested that "one photo a day" projects (like the 365 Days project on Flickr) are the digital age's version of marking your kid's height on the wall with a pencil.
If you're already a Flickr user, check out Project 365 Kids, which has been set up for parents to post pictures of their kids. You'll need to join the group to participate.
If you're not a Flickr user, or if you'd like the option of using a webcam, then Geekday recommends Flickaday:
"You can add a caption to each photograph, and there's even a feature that lets you transparently overlay yesterday's photo so you can match up features day-to-day."
Track Your Kid's Growth with Flickaday [Geekdad]