To be a great investor, you need access to accurate, high-quality information -- and preferably without having to pay an arm and a leg for it. With this in mind, I've scoured the Internet and plundered my "favorites" toolbar to identify and rank the 10 most indispensable websites for investors, many of which also happen to be free.

An image depicting the financial markets.

Image source: Getty Images.

10. Finviz.com
The importance of a good stock screener can't be overstated. A screener helps investors formulate strategies, guide research, identify and evade pitfalls, and compare companies within an industry and without, among other things.

There are multiple screeners available on the Internet, but most are either behind pay walls like Standard & Poor's Capital IQ, woefully inadequate in the case of Google Finance, or awkward to use such as the free screener at Yahoo! Finance. The most successful at navigating between these shortcomings is Finviz.com, a free screener that allows users to select and sort companies according to dozens of filters, ranging from fundamental statistics like gross margin to technical variables such as beta and moving averages.

9. Morningstar.com
After identifying a stock that interests you, there are any number of areas that should be investigated before buying it. To name a few, you'll want to learn about its financial condition and performance over the last few years, how much its executives get paid, and what they've said on recent conference calls.

One of the best free sources for this information is Morningstar.com, an aggregator of all of these things and more. It allows you to view normalized financial statements going back five time periods, access conference call transcripts, analyze executive pay and insider ownership, and survey any number of potentially important ratios and financial metrics.

8. YCHARTS.com
If a picture is worth a thousand words, then YCharts.com is worth the equivalent of the Oxford English Dictionary. One of my personal favorites, this site allows users to choose from among numerous financial metrics and economic variables and then chart them in an easy-to-understand and attractive manner.

7. MarketWatch.com and Renaissance Capital's IPO Home
I know that picking two sites for one spot is arguably cheating, but these sources satisfy two important niches, neither of which alone justified inclusion.

In the first case, have you ever read about a company that recorded positive top- and bottom-line quarterly growth but was nevertheless punished by traders because it failed to live up to analysts' estimates? If you have and then wondered what these mystical prognostications were, one of the best places to access them is MarketWatch.com, a financial website operating under The Wall Street Journal's umbrella. Enter a ticker symbol in the search box, select the "analyst estimates" tab, and then prepare to be transported to a paradoxical world where fortune-telling takes precedence over fundamentals.

In the second case, one of the great things about investing is the opportunity to participate in the growth of young and promising companies -- i.e., those that have filed an initial public offering, or IPO. The single best location for information on IPOs is Renaissance Capital's IPO Home, which provides pricing and valuation information on debuting companies as well as links to articles discussing the filing.

6. Fed's FRED
There's no better place on the Internet to access current and historical macroeconomic figures than the abundant database maintained by the Federal Reserve Bank of St. Louis. Known affectionately as FRED, this is literally the go-to source for top economic thinkers, financial practitioners, business commentators, and academics. Paul Krugman, New York Times columnist and economic Nobel laureate, has claimed to use it "three or four times a week, at least -- basically any time I'm addressing a U.S. macroeconomic issue."

The site contains chartable and downloadable datasets that shed light on unemployment, productivity, economic growth, credit costs, and exchange rates, to name only a few of the available topics. Indeed, if you've never had the opportunity to appreciate its wonders, then I highly encourage you to do so now. And if that whets your whistle, you can take it to the next level by exploring the Flow of Funds data on the website of the Fed's Board of Governors.

5. SEC's EDGAR
All of the sites I've listed thus far are secondary sources, taking data from other places and then presenting it into an easy-to-use format. While this service is necessary and convenient, sometimes nothing beats digging into primary source material. In this case, that means companies' filings with the Securities and Exchange Commission.

Every company that avails itself of the benefit of public markets is concomitantly obligated to file annual and quarterly financial reports with the SEC. The most important of these are the 10-Q (quarterly financial statement), the 10-K (annual financial statement), and the Definitive Proxy Statement, or DEF 14A, which precedes shareholder votes. The one place all of these can be accessed is the SEC's Electronic Data-Gathering, Analysis, and Retrieval system -- otherwise known as EDGAR.

4. Bloomberg.com
A Bloomberg terminal is the gold standard in terms of market data. But for investors who don't have an extra two grand sitting around each month for subscription dues, there's still Bloomberg.com, a free and invaluable source of high quality news and, yes, even data. In addition, I'd be remiss to exclude its sister site, Bloomberg Businessweek, a print and online publication of readable and high-quality business commentary.

3. Financial Times and The Wall Street Journal
Yes, this is the second time I've picked two sites to share one position. But trust me, if you're an active investor, one or both of these is virtually indispensable.

The Journal has great writers with unmatched access throughout the financial world. Beyond that, its Market Data Center is a great resource for information on individual company earnings and marketwide valuation multiples and dividend yields.

For analysis with a more global bent, not to mention the commentary of Martin Wolf, the paper's chief economics commentator, you could do a lot worse than the U.K.-based Financial Times. This is high on the shortlist for the finest sources of financial news and commentary in the English-speaking world.

2. Yahoo! Finance
If you're reading this, you're probably familiar with Yahoo! Finance, as much of our traffic comes courtesy of its ticker feeds. Yet many investors use only a sliver of what this diamond in the rough has to offer.

Enter a ticker into the search box, and scan the menu on the top of the page for a veritable feast of financial information. Want a listing of its SEC filings? Done. Analyst estimates for current and future quarters? Check. Insider ownership data? Yep. Financial statements? You get the point. Other than the next website on the list, I spend demonstrably more time on Yahoo! Finance's site than any other.

1. The Motley Fool
Last but not least, I can't help picking my proverbial home team as the most indispensable website for individual investors. Now, I know what you're thinking: "Of course he picked The Motley Fool; it is the company that cuts his paycheck." But hear me out here.

There are surprisingly few media companies that, like The Motley Fool, cater exclusively to the individual investor. Not only does The Motley Fool provide quality commentary and advice through our website and premium services, but we also regularly advocate before Congress and the SEC for the rights of investors, and offer CAPS, a free online investing community which allows its 180,000-plus members to track their favorite stocks, construct real and hypothetical equity portfolios, and interact with thousands of other people doing the same thing. Indeed, our motto is to "educate, amuse, and enrich," and we take all three of these components seriously.

The Motley Fool has a disclosure policy.