In this article:
http://www.ecmweb.com/ar/electric_pintsized_power_producers/
they mention using these generators in a grid-connected way. I have also read and heard about residential applications where you can use solar and/or wind power to "spin the meter backwords".

Has any of you ever done any of these types of installations? How does this work?

I noticed something in the article about sycronizing to the grid. How does that work? anyone ever done this?

I would love to at some point in the future (after extensive research and some training I'm sure) get into these types of energy conserving installations. I'm sure once you run the cost recovery numbers it isn't too hard of a sell. I think as our demand for energy increases and our supply decreases, we will eventually be forced to some of these trickier installations.

And just as a personal opinion, I think it is a disgrace to burn natural gas for nothing other than heat such as a furnace or hot water heater with out extracting electricy out of the burn such as in the types machines in the article. I'm sure there are collectively megawatts of power going up our flues every day (for those of us in natural gas areas) Every heat producing appliance should be a generator at the same time.