How about a diaper cake! I used to have a business making diaper cakes and sold lots of them, it was always the mom's favorite gift!
Here are a couple of photos of girl diaper cakes I have made in the past. (I've made bazillions!) I still have tons of supplies if you need help making one.
http://www.flickr.com/photos/____@____.com/2180959590/
http://www.flickr.com/photos/____@____.com/2180959274/
If you want to make one yourself to make it even more meaningful, you can find instructions online. You can do just diapers with ribbon and a cute topper, or you can really fill it up with lots of baby necessities like nail clippers, shampoos, lotions, baby powder, brush, comb, bib, mittens, socks, etc.
It makes a great practical gift because the mom will use everything on it (that is, if she has the heart to take it apart), but it's also a wonderfully creative way to present all those goodies!
A tip, I always use size 2 diapers so that the Mom can leave it up in the nursery for a while before having to take it apart!