Tonight, Cramer continued his "going green" segment after changing his stance on alternative energy stocks last night.

One he really likes is First Solar (NASDAQ: FSLR), which can compete head to head with traditional power companies in the fairly near future; he's liked it since March and it's up 30% in that time. MEMC Electronics (NYSE: WFR) is the other one he likes because they make the silicon wafers for solar panels; this one is up 200% since Q3 2006 and he has been positive on this one all the way up because there is a silicon shortage and the company is well-positioned to capitalize on it. Cramer did say that these names are all up big big, so what you really want to do is look for these on pullbacks when they get cheaper.

There is a much safer way (safe is a "relative term" only) to invest in alternative energy, and you won't be risking it all in a single speculative name. A few names I have looked at for exposure to "Alt-En" and that I feel better about are actually what I call the "Alt-En" ETF's, and these may offer you a safer mix of companies since some of the holdings are actually diversified and have many different operations. The PowerShares WilderHill Clean Energy ETF (AMEX: PBW), PowerShares Cleantech ETF (AMEX: PZD), PowerShares WilderHill Progressive Energy Portfolio (AMEX: PUW) will all give some alternative energy sector exposure that won't as easily rip apart your wallet if you make the wrong pick. ETFs will not give you the upside potential of a single speculative play, but if you've been doing this long enough, you already know how painful picking the wrong name in the right sector can be. Alt-En ETFs give you exposure to the sector without the company-specific risk.

Jon Ogg can be reached at jonogg@247wallst.com; he does not own securities in the companies he covers.