Besides storing them in hard disks, photo albums and other traditional ways, maybe can consider blowing it up into a portrait of sorts and incorporate it into the decoration of the baby room? Like this:
I took photos of them and blogged about it after my prenatal consultation! Have an online pregnancy diary in my blog and shared with my friends & family. I stored the hard copy in an album.
I pasted them in a self adhesive photo album. I shared them with my relatives but didn't post it on facebook.
I keep in my baby journal photobook by scanning a few clear ultrasound pictures and print out.
I read that over time it fades so I took pictures of them and blogged about them too!
thanks