ETFs are an extremely popular investment option, due to their low costs, diversified risks and accessibility. Here, Jonas Elmerraji looks at the various ways of investing in ETFs. He also recommends three small-cap ETFs for penny stock portfolios.

Tom Bulford says clean technology could become the “next big sector”. A growing awareness of environmental problems means huge investment in the industry over the coming years. And that means plenty of exciting start-up opportunities…

Every asset class has been beaten down by the 2008 credit crisis. But a market downturn means big gains for reverse ETFs. Eric Roseman says these funds provide a simple, cost-effective hedge against a bear market. He says the bitter experience of this crash should make reverse ETFs much more popular among diligent investors.

The garbage industry is about as recession-proof as you can find, says David Fessler. People won’t stop taking out the trash in a downturn. David says the Market Vectors Environmental Services ETF (AMEX: EVX) is a great way of investing in the sector, and is a bargain right now. For a specific company pick, he recommends Clean Harbors (NASDAQ: CLHB), which treats hazardous waste.

There are great wealth-creating opportunities in today’s miserable markets, says Andrew Snyder. Take oil, for example. The black goo is on a slippery slope towards $50 a barrel, and no OPEC production cuts are going to stop this in the short term. Andrew says the UltraShort Oil and Gas ProShares ETF (AMEX:DUG) is the best way to profit from the oil industry’s downturn.

Republicans like to call themselves the party of fiscal discipline. But Charles Delvalle says it’s actually Democrats who are more likely to reduce the federal budget. If Obama makes it to the White House, you may want to bet on a stronger dollar with the Rydex Strengthening Dollar ETF (RYSBX).

Long stuff up there on gold, so I’ll make this short. Where’s the shiny stuff going? Back in January, I told my Rising Tide readers that the Streetraks Gold ETF (GLD) was a smart buy. It’s certainly hit new highs since… and I think gold is an asset with long-term value for a bit of money. But…

The time’s right to short the iShares MSCI Germany ETF (EWG) says Sara Nunnally. She thinks it can’t hold it’s current level much longer - get in now before it drops faster than Gee Dubya’s popularity rating.

German ETF at point of no return; it’s now or never.

Editor’s Note: ETFs are revolutionizing financial markets, according to Money Morning’s Horacio Marquez. They allow investors to follow global trends without having to select individual stocks. They provide easy access to otherwise impossible-to-reach profit plays. And, by grouping stocks in a fund, they significantly reduce systematic risk in the market. For these reasons, Horacio says ETFs are the best way for investors to play today’s global trends…