Wikipedia: I Ching - http://en.wikipedia.org/wiki/I_Ching Information on the history, philosophy and structure of the I Ching and it's symbolism and use in divination.
Super I Ching - http://www.superiching.com/ This free I-Ching book is designed to allow you to predict just about everything: the death of a person, the exact time and date to expect a visitor, the rise and fall of the stock market, the presidential election, the out come of a war, etc.
Eclectic Energies - http://www.eclecticenergies.com/iching/findhexagrams.php Search facility, the trigram combinations in the classical grid and a list of all the 64 hexagrams of the I Ching.
I Ching Logic - http://www.ichinglogic.com/ Two I Ching Oracles, a simple one and a complex one, and a breakthrough explanation of the theory behind the I Ching.