There are so many definitions of what a green job is, that it's now getting to the point where it's difficult to know what a green job is. And the difficulty is increased by the lack of clear and agreed upon definitions of a green company and the categories of green products or services (is nuclear clean? is "clean coal" really clean?). 

So to add to the confusion, I'll add my 2 cents to the discussion.  A green job is:

• A job at an association or non-profit engaged in environmental matters.  You can research these associations easily at theGreenJobBank.  These include among many others: activist organizations, think tanks, and manufacturers associations.
• A job at a federal or state government agency protecting the environment (EPA or similar agency at the state level).
• A job at a technology startup company that works on renewable energy technology, or new recycling methods, or electric or hybrid automotive technology.
• A job at an established company (i.e. not a startup) that derives more than half of its revenue from green products or services.
• A job at an established company (small or medium) that employs more than half of its employees in green products or services activities.
• Finally there are green jobs at large companies like GE or BP that have entire divisions dedicated to renewable energy technologies, such as BP Solar or GE Energy.</li>