Well, there's obvious avenues for government investment and expansion within the green energy sector. There's a need for de-regulation of nuclear power. Over the long run, green sources provide a much cheaper cost/kWh, so there's savings to be had there. People are really over-rating how difficult it is to get away from non-renewable sources. Ontario has gotten off of coal (which in 2004 provided 25% of energy to the province) in less than a decade.
There's the potential for plenty of new infrastructure spending with regards to transit. More or less all building of roads should be suspended; they won't ease congestion, and capacity is much more cheaply provided (and environmentally sustainable) by building high-speed rail, light rail, trams, commuter rail, S-Bahn-esque systems, etc... Furthermore, rolling stock like that isn't built in the third world, so all jobs could be contained within the country of origin. Plus, transit, much more so than roads, offers superior and more sustainable economic development, which in turn decreases reliance on automobiles. With enough investment, major North American cities could be able to ban personal cars from much of the interiors of cities in a decade or so.