My pediatrician gave me a lot of free 'samples' of formula... if you are planning or even down the road use formula ask the pediatrician for samples. I ended up using a different brand then the doc's office supplied so I stop asking for samples. The hospital did give me a free 'diaper bag' with cans of formula in it... I was breastfeeding at that time but switched over a few months later because my daughter was lactose intolerant.
I also got a lot of free baby shampoo from the pediatrician which after 2 years I am still trying to use up.
I am not sure about free diapers, hope someone else can give you advice there.
Here are a few websites you might want to check out... not sure if they are all completely 'free' so don't give personal info until you feel safe with the site.
http://www.babytobee.com/affland.aspx?vid=99&ovchnGGL...
http://www.babycenter.com/freestuff.htm
http://www.bestfreestuffonline.com/
http://free-baby-stuff.yeahbaby.com/
Hopefully some of the other moms will say one of these sites they have used and liked.