Tirerack.com is a good place to purchase and review tires.
IF you live in a state that has sales tax. Here in NH where there is no sales tax…I can easily beat Tirerack’s prices. And I’d rather deal with a local tire store then with a large place that I can’t bring a faulty tire to.
I agree with Mike above. Tirerack.com has a wide selection and lots of feedback to help you choose. But it has been my experience that by the time you price out the final cost to have the tires shipped to you (or one of their preferred installers which may not be convenient to you), load and carry the tires, find and pay someone to install them, pay to dispose of your old tires, the savings is minimal.
If you buy 4 tires (at once) from me I’ll rotate them as directed by your owner’s manual, check and fill the pressure, and repair punctures for free. If you have a tread separation or other defect I’ll take care of you.
If you have 4 mail order tires, you’re just another guy dropping off your car for a flat repair.