I'll start off with the turn-key options.

[Westcliffe01]

If you take a look at this page http://www.sunpower.com/index.php?pg=22, you will find that a lot of activity has taken place at sunpower in the last 10 years and they have the IP legally sewn up pretty good.   There is a long list of patents they have been awarded.

The attached PDF lists the plans for commercialization, but always is dependent on external funding. Microgen has in fact been quietly selling the Sunpower engine based co -generation systems in selected locations and the cryogenic coolers are in production, but don't know by who.

[elnav]

Where I live in central BC there is so much pine kill wood around its free for the asking. Consequently many people now heat with wood.  If they could have a 2kW  Stirling genset mounted on top of  their wood heater they could have free power as well. We have six months of winter heating season so the wood furnace run 24/7  and so would the power generator. Even a modest battery bank would suffice to power an inverter to provide all the needed power.
BTWDuring mu search for Stirling motors I found an article dealing with how the swedish navy has a Stirling engine for propulsion. Apparently this engine can deliver 5 MegaWatts.  The combustion is supported while running underwater by using a liquid oxidizer for the burning of liquid fuel  much like some of the early rocket  engines did,