Congrats to your friend on birthing her little man.
A girl i worked with had her daughter at 25wks and she is perfectly healthy now (she'd be close to 1yr old), they had A LOT of time in hospital and it was very tiring for them so i think it's the little things that will help.

Are they going to stay at Ronald McDonald house or something similar, could you organise some meals to be taken to them?
A voucher for some premmie clothes, possibly even a visit from you once they are up to it, take her for a coffee or something?
A friend who's going through the same thing at the moment said the worst part is people don't know how to act around her, they don't ask how her son is doing in case the answer isn't perfect, she just wishes her friends would ask to go for a coffee or get excited to bring by the presents they'd bought (even if the clothes are WAY too big)....

Sorry prob no help at all...