Hello sean
I can tell you a couple of stores that I have ordered from in the past, although I don't believe they have free shipping. At least not under a certain amount. I don't wind up saving bookmarks of places that I have ordered from, so I don't have that many to post (there are just so many, there is no need for me to bookmark them).
Discount Hydroponics
The Verti-Gro Hydroponic Fertilizers and nutrients - Organic and Hydroponic Growing for Commercial and Hobby Growers (even though they are across the country from me the low cost of there nutrients is worth the shipping, and they do have a "shipping included" offer)
The way I look at it is when you get free shipping, they just include the price of shipping in the product, so you wind up paying for it either way. But to limit costs of shipping, I try to search for places close by where I live to order from. When you put quotation marks around a word/s, the search is narrowed to exact matches. And when you use a plus sign in the search, the results are limited to exact matches of the quoted keywords that include the added (+) word on the page/site. I live in Lake Havasu AZ (there are no hydro stores in my town), so the keywords I would use (if I was wanting free shipping) to search would look something like this:
"free shipping"+hydroponics+Arizona
"free shipping"+hydroponics+phoenix
"free shipping"+hydroponic stores+Las Vegas (because Las Vegas is about 4 hours away)
"free shipping"+hydroponics+stores+Las Vegas
etc. etc. etc...
To make sure there close to your location, just check there "contact us" page for a physical address (store location), and/or a phone number (other than a 800 number) that you can check the area code for a city location with,
Fone Finder query form. But if unlike me, your looking for free shipping, then location doesn't matter that much, unless you want to receive your package faster. Free shipping usually means slow (the cheapest shipping available). And the farther it needs to travel, the longer it takes. When ordering from a store close by (say within a days drive), I usually receive my package within 3-4 days, and without paying for expedited shipping. Just regular ground UPS, FEDEX etc..