Another one for Amazon here. I've written previously of some issues I'd had with my Kindle - they replaced it for free (no shipping costs either, and this was to Australia). The online chat service is amazing, and the rep. was extremely helpful. Amazon just do things right!
Also, Metagenics (health supplements). Rang the other day with a question from a patient, had a comprehensive answer from a specialist within a minute (literally!) and they then followed up with an informative fax, tailored to the particular situation. Any time I have to phone for info I can't find in the practitioner book, there is no waiting on the phone - all queries are dealt with in minutes. Extremely good service, and fast shipping of products as well.