While the best place to learn about Vampire: the Masquerade and the rest of the games in the World of Darkness is from the books published by White Wolf, there are quite a few sites on the web as well...

http://www.white-wolf.com
White Wolf Publication's website....check it out! You can buy the books, buy T-shirts, etc. or just talk to fellow rpers about the WoD in the forums. Great for keeping up to date on the World of Darkness. : )

Menohl's Hall of Sorrow
A great site....its got a character creation guide, a listing of disciplines, and the official Merits and Flaws. Just remember: as the author says, this is site is no substitution for the books. All this is just the tip of the iceberg! : )