I've had a few dealings with an online retailer now called firebox.com, and I've been constantly impressed with them - not only for doing things right, but also correcting things when they have gone wrong.
My latest experience is quite cool though. I'm on there mailing list, and haven't ordered anything from them for a while, so they sent me a mystery voucher. I typed it in on site and it came to £6. I was quite chuffed - £6 to spend towards anything with no catches. So I found a "pettree" for £5.95. Its a living cactus in a keyring.
So I placed the order, typing in my voucher code at the right point, and choosing the cheapest delivery they did - £3.95, bringing the total order up to £3.90 for goods and delivery with the voucher.
The very next day, the parcel company they use attempted to deliver my pet tree. They tried again yesterday succesfully as I made sure I was in. With the order came a free bag of sweets.
I'm left feeling slightly guilty as I'm very chuffed with my purchase and cannot see how they have possibly made money on it, so I thought in order to resolve these mixed feelings, and seeing as how a lot of the products they sell are Geek Friendly, that a mention on my blog may help me feel better about the transaction.