Find something you're truly interested in.
For ex, I love psychology and am interested in mental health, so I'm volunteering as a counselor at a crisis hotline. It's like the most ideal volunteer position I can think of, because I'm learning new things all the time, and I actually feel useful, since I'm doing "skilled" work. Of course, there's the benefit of having patient contact too-- everything from the depressed, to schizophrenics, to sex perverts. Good stuff, good times. 👍
The other volunteering I do is through an institute aiding new refugees to the country. I'm trying to learn Arabic, and thought it'd be a good way to get some practice at the same time. Did a web search, and found the perfect position!
Other things I've thought about doing: volunteer at the library (they have an ESL program for new immigrants, plus it's just fun to be at the library 😎), volunteer at a free clinic for Chinese immigrants, Nabuur.com (volunteer right from home!), volunteer teaching tennis to kids from low-income families, volunteer for Hillary's campaign, etc. etc.
So... don't know what you're interested in. But it's quite possible to kill two birds with one stone, and actually enjoy volunteering instead of just sit around being bored and feeling useless 😉.