Effective Altruism (EA) is a movement that attempts to maximize the good done in the world by appling critical thinking skills to charity and ethical action.
For the most part, you might consider yourself an effective altruist if you carefully consider a wide range of charities before giving or volunteering, research them carefully to determine which is the best use of your time and money, and arrange your life to better serve these causes -- by giving more, volunteering more, or otherwise improving the world.
The core values, as given on the EA homepage, are:
- Open-Mindedness: Consider all causes and actions, and then act in the way that brings about the greatest positive impact.
- Critical Thinking: Apply evidence and reason to determine the most effective ways to improve the world.
- Global Empathy: Value all sentient life, regardless of nationality, creed, ancestry, religion, or species.
Many effective altruists focus on donating the most money possible to the best causes possible. This involves, logically, improving their earning power as much as possible, and no small amount of the EA network focuses on career and money management.
Naturally, a large part of what effective altruists worry about is how effective it is to give to various charities -- how much money goes to the stated goals vs. to administration and fundraising, how effective the stated goal is in improving people's lives, how much benefit will be gained by marginal donations, the ethical theories underlying what we should give to... and so on. If you do not find this particularly interesting, there is a general consensus that Givewell is a good source for sound and uncontroversial recommendations.
One of the key aspects of EA is donating time and/or money, but you may also decide to improve the world by becoming a vegetarian/vegan (an easy way to support animal rights and the environment without spending much, if any, money), acting in environmentally friendly ways, becoming an organ/blood donor, or proselytizing the cause to your friends and acquaintances.
Resources and Further Reading:
Effective Altruism is the public face of the movement. The EA Forum has regular posts on matters of rational charitable giving.
The Givewell Site recommends charities by effectiveness. If they do not have information on the charity that you are interested in, you should check out The Charity Navigator.
80,000 Hours is a career guild helping you to determine how to do the most good through your work.