You could make her a little hospital bag- get a nice makeup bag and fill with tums, hard candy, mints, facial wipes, hair ties, lip balm, mini brush, mouthwash, a little back massager, fuzzy slipper socks with tread, and fancy mini bath products.
A gift certificate for a prenatal massage or a pedicure would probably go over very well in the third trimester.
Ditto PPs suggestion for meals or a maid if you can afford it- the first few weeks are rough and it's hard to do anything besides keep baby alive!