Protest Poems is not your run-of-the-mill prompt and share community. Subtitling itself "Writing Exercises with Meaning!," each month there is a new protest-inspired prompt (currently, the prompt is "Women's Voices"). They don't call for preaching or propaganda, but instead are devoted to the pursuit of free speech and human rights. After writing about the prompt, you can submit the poem for inclusion in an unedited compilation designed to spread the solidarity of unified voices standing up for human rights. Protest Poems makes a great effort to combine art and activism.
Protest Poems also has a PayPal account to which you can donate $1 to help defray administrative costs.