With thousands of stocks to choose from, the stock market can be daunting for new and experienced investors alike. Exchange-traded funds provide an easy way to instantly and affordably buy into whole sectors of the market, giving your portfolio much-needed diversification. But not all ETFs are created equal: Some charge needlessly high fees, while others focus on ridiculously specific and volatile sectors of the market.

On The Motley Fool's Twitter feed, follower Olavarrieta asked us which ETFs look best right now. In response, three fund-savvy Fools have given us their best ideas for ETFs that present ideal opportunities for long-term Foolish investment.

Just call him "Dividend Dan"
Dan Caplinger, Fool editor
With all the uncertainty in the economy and the stock market right now, I'm a big fan of dividend stocks with long track records of consistent, growing payouts to shareholders. High-yielding dividend stocks have historically produced better returns than low- and no-dividend stocks, and their payouts also help provide some protection against falling stock markets. Moreover, given how low interest rates are right now, dividend stocks are among the best strategies for generating income in today's market environment.

The easy way to get a full helping of great dividend stocks is through the SPDR Dividend ETF (NYSE: SDY), which owns around 50 of the highest-yielding members of the High Yield Dividend Aristocrats index. To be included in the index, a company has to have raised dividends annually in at least 25 consecutive years.

CenturyLink (NYSE: CTL), Eli Lilly (NYSE: LLY), and other powerful dividend-paying stocks have demonstrated their value to long-term investors. If you want to buy into stocks like those through a single investment, the SPDR ETF could be exactly what you're looking for.

All that glitters is ... well, silver, actually
Christopher Barker, Fool contributor
I'm not much of a gambler, but if I walk into a casino, I know better than to place all my chips on a single spin of the roulette wheel. That's the beauty of a well-selected ETF: It allows you to place chips more confidently upon a single bet, without putting all your eggs in one basket.

In the high-stakes world of precious-metal mining, investors face a whirlwind of potential risk factors: geopolitical uncertainty of mining jurisdictions, labor disputes, environmental impacts, permitting, variable ore grades, tightness of credit, mine construction and ramp-up delays, and of course, that dreaded volatility in market prices of the underlying products.

For this reason, I advocate a basket of precious-metal miners to spread that risk, while maintaining exposure to anticipated long-term price gains in gold and silver. For a number of reasons, I expect silver to produce even higher percentage gains than gold going forward.

The fairly new Global X Silver Miners ETF (NYSE: SIL) is by far my favorite ETF, especially since it owns shares of cash-flow powerhouse Silver Wheaton (NYSE: SLW), my top stock pick for 2010. I have staked my reputation on the future performance of this ETF, declaring that my associated CAPS pick will outperform the S&P 500 by 200% before I close my pick within the next five years. If you have strong opinions about the outlook for silver, or this ETF in particular, please vote in this Motley Poll and cast your own CAPS vote for this silvery ETF.

Built for the long haul
Amanda Kish, Fool analyst
When it comes to ETF investing, Fools, you want to go cheap and broad. Stay away from narrowly focused, pricier options that invest in one specific sector or country. These funds take on a lot more risk than most people realize, and there's usually no reason for the average investor to own such concentrated funds.

One of the best ETFs for broad-market coverage is Vanguard Total Stock Market ETF (NYSE: VTI). For a rock-bottom 0.07% expense ratio, investors can get a wide allocation to the domestic stock market, including both large- and mid-cap names, with a smattering of smaller stocks. To boost your small-cap exposure, the iShares Russell 2000 Index (NYSE: IWM) is a solid, reasonably priced option with relatively low tracking error.

Looking abroad, two of the most compelling ETFs for investors of all stripes are iShares MSCI EAFE Index (NYSE: EFA) and Vanguard Emerging Markets Stock ETF (NYSE: VWO). With expense ratios of 0.35% and 0.27%, respectively, these funds are two of the best low-cost, well-diversified foreign choices around.

Finally, for broad fixed-income exposure, nothing beats the iShares Barclays Aggregate Bond Index (NYSE: AGG), which invests in a wide range of government, mortgage, and corporate bonds. With just this small handful of ETFs, investors can get exposure to all the major corners of the global market.

We want your questions!
Thanks to Olavarietta and all the Foolish folks who've sent us questions via our Twitter feed. If you'd like a Foolish perspective on an investing or personal finance topic that's important to you, tweet it to us @TheMotleyFool or post it in the comments box below. Your question could become the focus of a future Fool article!