I have purchased tires on-line from the TireRack in the past but now I think you can do better at the local Mom & Pop tire store.
I used to live in Lynn, MA and my in-laws did business with a place called Bennett Street Tire (781-598-1613) -
http://www.bennettstreettireglass.com. These guys buy up odd lots of tires when they can at considerable discount and pass the savings on to ther customers.
I was shopping around for new tires for my Chevy truck (P265/75R16). I was looking at the Bridgestone and Michelin dealers, but they wanted over $160 per tire. Bennett Street hooked me up with Goodyear Wrangler RF-A (Rotation Free Aquatred) tires for
$90 per tire installed. NTB or the Goodyear dealer would have been around $140 for the same tire.
The tires have worked great so far. They look sharp and ride better than the original P245/75R16 Goodyear Wrangler RT/S tires too.
It pays to shop around!