Here's an article from Investor's Business Daily that talks about recent trends in venture investing.
Notably, there's this quote from Matt Garlick, research director at VentureOne:
"The two most popular areas we are hearing about are in energy and advanced specialty materials and chemicals."
Not exactly a direct hit on cleantech (clean energy, clean manufacturing, advanced materials, etc.), but a pretty good proxy... And the article goes on to note that analysts are projecting that demand for energy-producing and energy-saving technologies will only grow from here.