I urge everyone to visit the website Causes, where you can make a difference without even leaving your home. By signing up (it's free), you can sign petitions, make pledges, and donate to a wide array of important causes relating to animal and human rights, environmental protection. and more. It is an awesome and simple way that you can do your part to make the world a better place.
Here is one petition that I recommend everyone sign, which urges Congress to create a national law that makes the gassing of animals as a method of euthanization illegal (It is often a slow and painful death for the animal).