Exchange-traded funds - described by About.com's Dustin Woodard as similar to index mutual funds, but traded more like stocks - are investments growing in popularity and worth understanding. These sites help you do that.

About.com.

First, here's Woodard's informational page on ETF basics, which provides notes on some advantages and disadvantages. For example, the funds can be bought and sold through the trading day, unlike mutual funds, but you pay a commission on every trade:

http://mutualfunds.about.com/cs/etfs/a/exchangetraded.htm

ETF center.

Yahoo's "education" page on exchange-traded funds examines frequently asked questions and explains such things as how fund managers must lay the groundwork for ETFs and submit plans for them to the Securities and Exchange Commission, why there are tax advantages, and why they appear to be much more than a passing investment fad.

education

SEC central.

The Securities and Exchange Commission offers basic advice on ETFs that every investor ought to take a refresher in from time to time - in particular, you should ask for a fund's prospectus and read it, along with any other information you can get hold of about the fund.

Star power.

Morningstar Inc. is famous for its guides to the thousands of mutual funds. Now it also tracks exchange-traded funds and offers a selection of primers on the subject. You do have to register (free) to access the material. The site is peppered with advertising for Morningstar's paid reports and newsletters, but you do get access to a selection of commentaries from its analysts and to the charts for individual funds.

Financial Times.

The Web site of the peach-colored Financial Times newspaper is a good place to read news reports about exchange-traded funds and the companies behind them.

Contact staff writer Reid Kanaley at 215-854-5114 or rkanaley@phillynews.com.