Whether you're a passive investor or a very active investor, Exchange Traded Funds, or ETFs, can be an important tool to meet your investing goals. ETFs provide low fees and track indexes with defined portfolios that behave predictably on the market.

The Nasdaq is one of the largest providers of indexes that ETFs follow worldwide. Here are a few Nasdaq ETFs that investors should keep on their radar.

Betting on the Nasdaq 100
The Nasdaq 100 is probably the most well known index in Nasdaq because it contains the largest domestic and international non-financial companies listed on the Nasdaq Stock Market. Given the size and stability of companies like Apple (NASDAQ:AAPL), Microsoft (NASDAQ:MSFT), and Amazon.com (NASDAQ:AMZN), which are the largest components by weight of the Nasdaq 100, the index is a fairly conservative collection of stocks. 

But there are a number of ways to bet on the Nasdaq 100 and not all of them are so conservative.

  • PowerShares QQQ (NASDAQ:QQQ): This ETF aims to track the Nasdaq 100 and also happens to be one of the largest ETFs by assets under management in the U.S. The fund has $39 billion in assets under management and is a favorite of investors large and small. 
  • ProShares Short QQQ (NYSEMKT:PSQ): Betting that the Nasdaq 100 will fall is the PowerShares Short QQQ. Like its name implies, it is short the stocks in the Nasdaq 100.
  • ProShares UltraPro QQQ (NASDAQ:TQQQ): If you really want a thrill, the ProShares UltraPro QQQ aims to replicate three times the daily move of the Nasdaq 100. But remember, replicating a multiple of daily moves sends an ETF lower long-term (something I'll explain below) so this is an investment that's designed to be held short-term.
  • Proshares UltraPro Short QQQ (NASDAQ:SQQQ): This is just the short version of ProShares UltraPro QQQ, moving three times the inverse of the Nasdaq 100 daily.

No matter which way you think the Nasdaq 100 is going to go there's an ETF for you.

Specialized ETFs
Some of the most interesting ETFs following Nasdaq indexes are in very specialized sectors that investors should definitely keep an eye on.

  • First Trust Nasdaq Clean Edge Green Energy Index Fund (NASDAQ:QCLN): This clean energy fund owns a number of major clean tech companies like:
  • PowerShares Global Water Portfolio (NASDAQ:PIO): Invests in companies that "create products designed to conserve and purify water," a growing business both domestically and around the world. 
  • PowerShares Golden Dragon China Portfolio (NASDAQ:QQQC): This index follows companies that generate most of their revenue in China. Top holdings include Ctrip.com, NetEase, and Baidu. 

With these three stocks you can get exposure to the growing Chinese economy, water infrastructure, and clean energy. But there are other specialized ETFs that may interest investors.

Beware of the leveraged ETF
What's the problem with holding leveraged ETFs long-term? Since they're leveraged to the daily returns of an index the fund will go to zero over the very long-term. This may take years or even decades to happen and some leveraged ETFs have gone higher for years at a time, but every daily leveraged ETF will underperform a multiple of the long-term returns an index has. I went through the math showing why in an article here

Just keep that in mind whether you're investing in commodity, market, international, or any other kind of leveraged ETF. There are dangers in holding it for a long period of time. 

ETFs are a new favorite for investors
Because of the passive nature of ETFs, investors have been piling into these funds for a decade now. Through Nasdaq indexes you can invest in a variety of classes of stock, commodities, or even specialized investments. 

If you're looking for a Nasdaq ETF that has the characteristics you're looking for check out their full list of ETFs here. There might just be one for you.