There are few things more rewarding than knowing you have helped somebody achieve their goals and work towards living a better life. Social work is so multi-faceted that you can work in many areas of the field and find a niche for you.
The position is very stressful and tends to be low paying, since Social Work is a non profit industry. You have to be passionate about what you do, since that will be what gets you through the day.
I worked in an NGO in China, specialized in homosexual rights. Most of my job involves translating foreign LGBT (lesbians, gays, bisexuals and transgenders) news into Chinese. It helps a lot of LGBT people in China. It is quite meaningful for me.