Diapers

There are two great ways to get CHEAP diapers. 
1. Target diapers are great and about the cheapest I've found. 
Size 2  $0.156 per diaper
Size 3 $0.138 per diaper
Size 4 $0.162 per diaper
Size 5 $0.185 per diaper
Wipes:
Regular  $0.017 (not even 2 cents each)
Sensitive $0.019 (still not even 2 cents each)
You can buy online and get free shipping if you spend over $50!

2. Amazon Mom is a great way I've found to buy name brand diapers.  Yes, there is a difference.  Some of the name brands have special designs for preventing blow outs and for sensitive skin.  They aren't perfect either, but for those of you who prefer them, here's a cheap way to get them:
(Thanks Kalie!)

If you sign up for automatic deliveries of diapers (and you can cancel at anytime) they come at a great price.  You can also get cheaper wipes too.  And, you can usually get prime 2 day free shipping on almost everything now.

Here are some examples of prices:

Huggies:

Size 2: $0.19 each

Size 3: $0.21 each

Size 4: $0.20 each

Pampers:

Size 2: $0.18

Size 3: $0.28

Size 4: $0.19

Wipes: $0.02