I've been looking everywhere for a birthday book, aka perpetual calendar, which is a book where you write down people's birthdays by month. I'd seen one online that I was going to order (for $9.99 plus shipping), but their only shipping method was UPS, which doesn't work for me.
I found myself at CVS today and they had those free little Hallmark calendars at the register. I picked one up and realized -- aha! -- there's no need for the calendar to be undated! So I took one of these cute and slim little calendars and will write down all the birthdates of my friends, and their increasing numbers of offspring (very hard to keep track of), and can tuck it into my little day planner. What a nice solution -- especially because it was free to me.