Some resources that may come in handy:
Greenpeace International's Guide to Greener Electronics - Ranks manufacturers of computers, mobile phones, TVs, and game consoles according to their policies on toxic chemicals, recycling, and climate change.
RoHS logo - An indicator that a product complies with the European Union’s Restriction of Hazardous Substances, which restricts the use of 6 hazardous materials in manufacturing: cadmium, hexavalent chromium, lead, polybrominated biphenyls, and polybrominated biphenyl ethers.
Energy Star label - Indicates that the product is energy efficient, conserving electricity use, and reducing greenhouse gas emissions linked with energy production and use.