Quicken, One of the most in depth and simple stock screen tools available
NasdaqTrader, The best source for up to date info on the nasdaq.
Fidelity Investments - In my humble opinion, the single best discount brokerage firm to do business with.
The Motley Fool, Tom and Dave have lots to offer here.
Chicago Board of Options Exchange, THE place to trade.
Chicago Mercantile Exchange
Good place to go for real time alerts about companies and economic indicators.
Great source for companies outside the United States. Great for a story of the small investor. Drips at their finest. Smart Money Online Every Known Stock Exchange To Me