What's tea without water? Well, it's still tea but it sure doesn't go down as well.
My point being that a good cup of tea really only has two ingredients - unless you like to desecrate yours with milk, sugar and whatnot. That said, it's in your best interest to make sure that you're using good water to brew your tea.
Tea Guy swears by a Brita pitcher for all water drinking and tea making needs, but if you're one of those bottled water types here are some resources you might find useful.
The Bottled Water Store - Features a Water of the Month Club and waters from about sixty different manufacturers.
Mineral Waters of the World - A site maintained by a Swiss gent with no apparent connection to the bottled water industry. He says, "My aim is to create the largest database of bottled waters in the world and a valuable resource in finding your favourite water."
Fine Waters - This one is described as "a site designed to be the definitive voice for water connoisseurs and their accompanying lifestyle."
And a few industry sites:
International Bottled Water Association
Canadian Bottled Water Assocation
The Australasian Bottled Water Institute Inc.