Exchange-traded funds are hot. There are currently about 290 ETFs available to investors, but that figure is predicted to double in 2007. Billions of dollars -- literally, billions -- are flowing into ETFs every week.

While that growth is eyebrow-raising, the proliferation of ETFs has made choosing the right one(s) for your portfolio overwhelming. That's why we asked for your help last week in selecting the best ETF for 2007.

Hot, hotter, hottest
About the only things hotter than ETFs in the investing landscape right now are foreign equities. Superinvestors Warren Buffett and Jeremy Siegel have said that U.S. investors would do well to look abroad for the world's best stocks.

So it may not be a surprise that investors using our brand-new Motley Fool CAPS community intelligence database voted the Vanguard Emerging Markets Index (AMEX:VWO) the best ETF for 2007.

The holdings in the Vanguard Emerging Markets ETF are concentrated in the fast-growing economies of Brazil, China, India, Korea, Russia, South Africa, and Taiwan. Since inception in March 2005, the ETF is up 48%, which speaks to the incredible potential of these markets.

With greater reward, of course, comes greater risk. But VWO mitigates that risk by holding more than 860 names spread across 23 nations. Some of its heftiest exposure is to PetroChina (NYSE:PTR), Petroleo Brasileiro (NYSE:PBR), and Taiwan Semiconductor (NYSE:TSM). In addition, its 0.30% expense ratio is a dirt cheap way to gain foreign exposure.

While many U.S. companies generate substantial revenues overseas -- Microsoft (NASDAQ:MSFT), for example, derives a significant amount of its revenue overseas -- there's a clear need for American investors to go global in their portfolios.

VWO in '07
As Foolish colleague Dan Caplinger argued, "As a portion of a well-diversified portfolio, the Vanguard Emerging Markets ETF can be a great way to broaden your investment horizons and take advantage of the growth opportunities in some of the world's most dynamic economies."

Judging by the CAPS votes, many Fools agreed. The majority of folks have rated VWO "outperform" -- it's a five-star ETF -- and it's more highly regarded than the 10 other ETF contenders.

So there you have it
The closed-end fund H&Q Life Sciences Investors (top holding: Gilead Sciences (NASDAQ:GILD)) came in second, while the iShares Russell 1000 Growth Index (top holding: Microsoft) finished in third.

Neither ETF promises the explosive growth of emerging markets -- but biotech and large-cap growth are no slouches. To read the analyses on all our ETF candidates, click here. And for help finding the right one for your portfolio, see what investors are saying about the fast-growing ETF offerings over at Motley Fool CAPS.

Thanks to all who voted, and congratulations to the emerging-markets folks at Vanguard.

Brian Richards owns shares of the Vanguard Emerging Markets Index ETF and Microsoft. Microsoft is an Inside Value recommendation. The Fool's disclosure policy is really quite informative. Really.