DIY spring dress bookmark (with tutorial). I like this idea a lot. Inexpensive, rather easy, and I have most of the supplies already at home (and trying to use up). Make a variance to this by using my niece's name, or an object she likes. Place in book.
Sometimes the simplest ideas are the best! What a cute little piggy bank. Great idea for monetary gift giving too. - Get the free pattern to make a whole mess of felt piggy banks. Easy, cheap and a great little gift!