Doing your homework and checking data yourself is essential for successful investing. What you may not know is that you no longer have to pay for comprehensive online information.

Yesterday, the folks at FINRA -- the Financial Industry Regulatory Authority, which was created in July through the consolidation of the NASD with certain regulatory divisions of the NYSE -- launched a free online service chockfull o' content for the retail investor. The Market Data section of FINRA's site includes data on equities, indices, options, mutual funds, and bonds. The site provides calendars of economic indicators and Washington events, as well as market news headlines.

The site is an investor's playground, containing individual security and market stats in easy-to-read tabular formats. If you want to know the latest, let's say, on the latest toy recall by Mattel (NYSE:MAT) or Kraft's (NYSE:KFT) earnings, just enter the company's ticker to bring up all the latest news, as well as a list of all securities issued, option activity, and access to SEC filings. Mutual funds are categorized and accessed by categories such as performance, portfolio characteristics, and fees, and you can compare expenses of funds and ETFs.

While many of these features can be found on other sites, such as the finance section of Yahoo! (NASDAQ:YHOO), one of the nicest features of FINRA's Market Data is that it's commercial-free, so you don't have to contend with annoying pop-up ads or flashing banners vying for your attention. You can maintain your own watch list and even check out your broker or security firm's background by clicking on Broker Check before picking up the phone to place an order.

Not just stocks
For fixed income investors, bond coverage is particularly exciting, with more in-depth data provided than is usually found even on major financial websites. Corporate, muni, Treasury, and agency bond info is supplied, along with benchmark indices of investment grade and junk bonds. Real-time transacted price info is given for both muni and corporate bonds, as well as the issuer's credit ratings. Searches can be conducted for individual bonds using an array of criteria, including price, yield, coupon rate, maturity date, callability, tax status, and credit ratings.

Particularly during these days that try an investor's resolve, FINRA's new service is welcome. If the market continues to slip, use of this free resource may be one way to eliminate needless expenses while leveling the playing field for the retail investor.

Yahoo! is a Stock Advisor pick, while Kraft is an Income Investor pick. 

Fool contributor S.J. Caplan is an arbitrator for FINRA. She owns shares of NYSE Euronext. The Fool has a disclosure policy.