I recently found Climate Solver on WWF's Swedish website. It showcases 12 young entrepreneurs who are coming up with environmentally businesses. Their solutions are varied and focused on solving one particular problem related to energy production, energy efficiency, construction, transportation, and system innovations. See 12 Climate Entrepreneurs for a white paper on their products and services.
One of the companies, Parans Solar Lighting has concept that struck me as a very realistic option for existing buildings with deep floor plates or no windows (sadly, we have a number of these in Washington, DC). Parans fixtures use fiber optics and LED technology to harvest natural light and save 50% of the energy typically required to light buildings. Considering that lighting is the largest impact on energy use (hence energy cost) for most office spaces, this is a significant savings.
Images from Parans' website.