I give you...da-da-da...the Birthday Book!
Get a really nifty (and large) sketch/scrapbook. Have everyone (parents, sibling, and kid, even) write/draw/be creative on a page for each birthday; this is the perfect age to start at, 'cause she's old enough to get the idea, just! This year it'll be kind of small (include a special page at the front describing/explaining it), but over the years, it will become a real treasure for the whole family.

(Not entirely my own idea; modified from someone else's that I read about in Family Fun magazine. :)