There are several organizations that have action campaigns setup to give you an opportunity to make a difference and envoke change:
National Women's Law Center: An organization using the law in all its forms: getting new laws on the books and enforced; litigating ground-breaking cases in state and federal courts all the way to the Supreme Court; and educating the public about ways to make the law and public policies work for women and their families.
Women's Sports Foundation: The leading authority on the participation of women and girls in sports—advocates for equality, educates the public, conducts research and offers grants to promote sports and physical activity for girls and women.
AAUW: Advancing equity for women and girls through advocacy, education, and research. The AAUW breaks through educational and economic barriers so that all women have a fair chance.
Now! National Organization for Women: As the largest organization of feminist activists in the United States, NOW's goal has been to take action to bring about equality for all women. NOW works to eliminate discrimination and harassment in the workplace, schools, the justice system, and all other sectors of society; secure abortion, birth control and reproductive rights for all women; end all forms of violence against women; eradicate racism, sexism and homophobia; and promote equality and justice in our society.
Girls, Inc.: A national non-profit youth organization dedicated to inspiring all girls to be strong, smart, and bold. With roots dating to 1864, Girls Inc has provided vital educational programs to millions of American girls, particularly those in high-risk, underserved areas. Today, innovative programs help girls confront subtle societal messages about their value and potential, and prepare them to lead successful, independent, and fulfilling lives.