Tires (and oil) are probably the things I spend the most money on for my cars. The differences between a budget set of tires and a good set of tires can mean life or death in certain situations. My last few sets of tires have been purchased through TireRack.com, and I can't recommend them enough. Their prices on 'good' tires (I see good tires as name-brand, high positive review tires - think Continental, Goodyear, Michelin, Hankook, Yokohama, etc.) are often some of the lowest you can find and their selection is unmatched. You can buy the tires online and have them shipped to an authorized installer who will receive them, call you to set up an appointment, and only charge you for installation. You can even have the tires mounted on rims by TireRack and have them shipped directly to your door (that's what I did for my set of winter tires - I had them mounted on dedicated steel wheels and shipped to me. I can swap to winter tires in 20 minutes at home).
Their customer service is unmatched. Case-in-point: I ordered the aforementioned snow tires online and within 5 minutes I got a call from a specialist (not a salesperson) to remind me that the tires would be shipped with special lugs for mounting them (can't use the factory ones on steelies) and also to tell me that the tires I bought were the ones best suited for the car I was buying them for. They will also work to resolve disputes with the installation shop if there is an issue and their tires have lifetime road hazard protection.
Sorry for the spiel. I promise i'm not affiliated, I just think they're a great business.