A few other things to add:
Support the people who are the front lines of grief, providing support to the bereaved. This is particularly applicable for those who are not in a good position to support the grieving parents, i.e. a hugely pregnant sister-in-law is probably not the most welcome guest in times like these. Not her fault, but it is what it is. She can, however, water the plants and collect the mail for her mother, who is on the front lines comforting and caring for the family members in crisis.
Pop in at four or six weeks and offer to scrape all the dried out, no-longer edible casseroles and gifts of food into the trash. Cleaning out the fridge is an unbelievably daunting process, and remembering each visit and blundering well-intentioned person who brought the food in the first place can be painful reminders.
Seek out others who've been through what you're going through: online, in person, in support groups. I only wanted to be around people who'd been through the kind of grieving I was doing for a while. I make a geeky reference to Harry Potter to try to describe it. In the Harry Potter books, there are magical creatures called thestrels. They are gentle, horselike creatures that are invisible unless you've seen someone die. Some people can see thestrels (Harry, Luna Lovegood, Nevin Longbottom); some can't. I only wanted to be around people who could see thestrels for a while.
Oh, and never say, "Your child is in a better place." There is no better place for a cherished child than with their parents. Even if you fervently believe that God must have needed another angel, just zip it, for now.
And maybe, just maybe, link to this post or sum up the comments and post them on other online parenting forums not dedicted to the babylost. The Bump, Mothering dot Commune, Baby Center, Parenting.com.... You never know who will click on this. The well-meaning friends and family members who need these tips so desperately won't know how to find them when they first get this kind of news. Maybe gently sharing them in other forums will help someone be prepared in ways they can't know when they first click on them there.