I've been using Walmart's free delivery* service for a few months now. It's great for staples but, of course there's no 'fresh foods' available that way. I get that from my nearby grocery. The Walmart prices are often better than the US Amazon prices.
With Amazon lately I've seen no shipping charges even with purchases less than $25...U am a Prime member. Don't know if this is new policy or because I use my Prime Points but is definitely different from before.
*(free delivery with minimum purchase)
Edited to add: they tout 'two day delivery', however, at least here that means only if the item is in the local Walmart...anything other than that can take up to a week. Sometimes my order will come in four separate shipments on different days depending on where the items originate.