i found a thermos mug incredibly useful! i got really sick of re-heating cups of tea in the microwave - they never taste the same! it's a bit practical but great for the early days when you can never predict when you'll have long enough for a cuppa! pair it with some yummy cookies and that's make me smile!
This is a bit cheesy but I was skint when my friend had her LO so I gave her a home made voucher book with things like a manicure from me, dinner at my house, I would do her shopping for her for a couple of days, half a day babysitting while she did what she wanted etc just daft little things. She seemed to appreciate it. Although I wish I had put an expiry date on them.....
cake gin meals for the freezer - a lasagne would be wonderful offer of babysitting the older child if she has one - well not babysitting as such but taking them on an exciting trip to the park etc to give her and the new baby some time.
in general new mums appreciate thoughtful things that will make their lives easier rather than expensive 'gift items'