I can see a real usefulness for National Green Pages and iRecycle.
I'm a little up-in-the-air on LiteFaire and GoodGuide, maybe because I see buying new types of light bulbs & grocery shopping as an activity that I plan for first, & only perform if I'm working off of a list. If they had a desktop app available as well, that'd probably be more useful... but that's just my personal preference.
greenMeter...seems kind of more like a game to me. Unless you know how much to tilt your smartphone so that its acceleration matches the acceleration of your car, and make sure that the app is aware of the vehicle you have (i.e. it doesn't confuse a 2010 Chevy Cobalt 4-cylinder with a 2002 Chevy Malibu V6), the app's results aren't going to provide even a good baseline comparison. Plus, there's the whole legal & attention issues with using your smartphone while you're driving...
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