I am with everyone on the diaper thing!
Also a great gift idea, especially for a first time mother, buy a journal. Ask everyone at the babyshower to write their motherly advice to the mother to be. Then give it to her after the shower.
For babies, I say the more layettes at night the better. Makes night time changings so much easier when you don't have to mess with snaps!
I had a friend who had a babyshower but didn't need much. So we gave her a diaper and dinners shower. Everyone brought a pack of diapers and a meal that she could store in her freezer. All she had to do is warm up dinner for weeks after the baby came.