City of Ellensburg, Washington, is one of the few municipalities in the US that still owns all of its own utilities (water, gas, sewer, electricity). It's also no coincidence that it was also the first city to build a community/utility owned solar array in 2006, feeding the community grid. It began generating power in November of 2006, and has since produced more than 170,000 kilowatt-hours, averaging 58,000 kilowatt-hours, annually. They're constantly expanding the array, and as of this fall, started adding wind turbines.
Grist is reporting that Boulder, Colorado, is investigating the formation of its own,publicly owned municipal utility. They initiated the study with a climate action plan passed by the city in 2002, committing it to reducing its emissions in line with Kyoto targets.
In 2006, the city imposed a carbon tax and just last year extended the tax by five years. Nonetheless, the city is falling short of its targets, in large part because it gets its electricity from the big private utility Xcel, which gets 60 percent of its power from coal (as of 2011). The idea behind forming a municipal utility would be to buy more renewable energy and have more direct control over pricing, distribution, and demand-side programs.