Internet is full of information sources for stocks.
Here is a list of websites I refer to the most:
1. Yahoo Finance: Yahoo finance is one destination which aggregates every thing from stock-market related news to SEC filings to stock-quotes for many years. They provide a rich set of APIs to query their servers. It is the only yahoo property which I like more than google.
2. Google Finance: Google finance lags yahoo in terms of information but their feature-set is definitely compelling.
3. stockcharts: I want to look at different stock charts and their patterns regularly and stockcharts provides a very rich set of overlay and technical analysis.
4. wikiinvest: wikiinvest is like wikipedia for stocks, but it offers more. They allow importing the brokerage account directly into the account and show their worth, trends, news all at one place and for free!
5. Fool: Fool is good destination to look for news and has a strong community of passionate stock traders and investors.
6. zacks: Zacks is a good portal which provides an in-depth analysis of stocks.
7. seekingalpha: Seekingalpha is another source of news but they have a number of cool features like adding Apps to your profile. This can allow getting all the news and reports all at one place.
8. gummy_stuff: Contains some cool stuff by a former maths profs from statistical information to spreadsheets for maintaining portfolio.
9. stocktwits: It has an interesting iPhone app to get twitter updates on stocks.
10. bloomberg: Last but not the least, bloomberg is a good website for news related to stock-market.
You can always look for interesting sites online related to stocks by looking at what people bookmark!