Others have had some really great ideas, but what about getting not only a "baby" present, but a present just for mom? I got a friend a body pillow to help her be more comfortable in the end stages of pregnancy (when it's so uncomfortable to sleep), but anything that pampers mom would be good...gift certificates to get hair, nails, facial, massage, etc., or maybe bath and body things.
Or you could always give yourself (always a very special gift because it comes straight from the heart and requires effort on your part)...make a book of coupons for things she might need now or once the baby arrives. You can make pretty coupons and decorate them and make them redeamable for things like free babysitting for a few hours (so she can run errands, take a shower, sleep without interuptions) or free dinner (you can make a casserole and all she has to do is heat it) or an offer to run errands, shop, pick up videos for a movie night at home, whatever SHE could use. It's always hard to find time for yourself and things like this are always helpful.