When I had my baby shower (I had 2 thrown for me), I couldn't get enough diapers. It's not a fancy gift, but it's super handy because brand new babies go through so many diapers and it was nice to have a diaper arsenal on hand rather than have to run out to the store. Baby clothes and booties and blankies are fun (I got tons of that stuff too) but the best gifts were the practical ones.
Another gift I received that I loved was this bouncy little baby seat. Not the swing, but a small gently springing seat I could easily move. I'd put my son in it and I could have him with me in the kitchen when I'd do the dishes, or take him with me to when I'd hop in the bath and not have to worry about leaving him in his crib (you'd be surprised how on edge moms can be when it comes to having to mommy bath time and not wanting to leave the baby alone in his crib).
Other good gifts that aren't fancy but very practical - bottles, bottle scrubbers, mylicon gas drops (that shit's expensive and mom dad and baby will need it for sure) lots of diaper rash cream - putting together a little care package with things baby needs are the best gifts in my opinion. Then again that's just me.
And Jeanie's right. Mom (and Dad) are often forgotten. Mom would probably like a gift certificate for a spa or hair cut so she can pamper herself because she's going to look and feel like crap after the baby comes. Or offer free babysitting and a gift certificate for a nice dinner out so mom and dad can have alone time and get away for a bit.