I can't do more than scratch the surface here -- I'll return to this topic more fully in a later column -- but some companies that deserve a place on your radar screen include DuPont (DD:NYSE - news - research - Cramer's Take), which has set a goal of making 25% of its chemical products from biological raw materials by 2010; General Cable (BGC:NYSE - news - research - Cramer's Take), which is producing new types of electric transmission cable to address a huge conservation opportunity (distribution losses in the U.S. electrical grid have climbed to 9.5% today from 5% in 1970); and Zoltek (ZOLT:Nasdaq - news - research - Cramer's Take), which makes high-performance carbon fiber used in autos and windmills to lower weight and increase strength.