He's an American icon from decades past who's managed to stay relevant by singing with Jessica Simpson and performing on Stephen Colbert's holiday show. And although Willie Nelson's body of music and movies is impressive, it's really his dedication to activism that really stands out to me.

Nelson's biggest achievement to date is founding Farm Aid along with fellow musicians John Mellencamp and Neil Young in 1985. Although it started as a simple benefit concert, it's since turned into a huge organization that has raised more than 33 million dollars. With giant corporations edging out small family farms, the foundation's goal is to help these small farmers and prevent their land from being developed. They also support organic farming and create awareness about buying local to support the farms' hard work. Today the three founders sit on the board of directors along with musician Dave Matthews (among others). Recently, as President of Farm Aid, Nelson even wrote a moving letter to President Obama regarding the importance of family farms and eating fresh, local food. And the tradition of the benefit concert has continued with an annual music show where dozens of superstar performers eagerly participate.

In addition Nelson is also passionate about horses and supports Habitat for Horses, which rescues neglected and abused horses as well as those headed to slaughter. He's also written to congress in support of the American Horse Slaughter Prevention Act.

But what I find the most intriguing is his interest in biodiesel, a clean-burning fuel that can replace regular diesel in the giant, gas guzzling trucks that cross the continent. It all started with his wife filling her diesel Volkswagen Jetta with restaurant grease. Then he bought a Mercedes and filled it up with 100% vegetable oil from grease traps. He loved the gas mileage, loved how the car ran and didn't mind that his tailpipe smelled like French fries.

Quoted as saying "There really is no need going around starting wars over oil. We have it here at home," Nelson is trying to change the way we see fuel. Made with vegetable oils, his company's BioWillie fuel can be used without any modification to diesel engines and is being marketed at truck stops. The benefits are three-fold: it reduces our need on foreign oil, it's environmentally friendly and it can help profit farmers. Which, of course, stems back to Nelson's original activist roots.