Everyone has a concern she'd like to support. Some of us have many of them. You don't always have to give money to a cause close to your heart. You can give time and effort. If you're an author, you can give short stories (or non-exclusive rights to a short story, which means you can also use it personally, if you'd like to) to charity anthologies that will benefit a good cause.
Many authors do free short stories as promo anyway. Why not earn money for a cause you care about along the way? That was my thought process. Even if you wanted to earn money on an anthology short, most anthologies are going to pay you $25-50 plus author copies for your piece. You not only get the exposure of a free read (or the loss of only $25-50 you would have conceivably made, which you can make up later with nonexclusive rights), but you get to do some good, on the way.
What anthologies or sites you'd submit to depends entirely on your genre and your causes. Sites like Simecenter take spec fit art and writing. Allromanceebooks is doing a call for sensual and erotic romance stories to benefit the American Heart Association. And so forth.
But one of my favorites is Coming Together. Coming Together anthologies benefit everything from Hurricane Katrina and SOCal wildfires to autism, breast cancer, HIV, and premature babies to stopping violence against women. In these anthologies, editors, authors, and cover artists take nothing. All proceeds are donated to the cause.
So far, I'm involved in three Coming Together anthologies--Coming Together: Under Fire (which benefits the SOCal wildfires), Coming Together: Against the Odds (which benefits Autism Speaks) and Coming Together: Into The Light (which benefits V-Day, fighting violence against women...coming January 2010).
If you enjoy erotic romance and erotica, consider scanning the Coming Together site and finding a cause you might want to support by buying an anthology of great erotic fiction. If you're an author, check out the calls for coming anthologies; you might find a cause you'd like to support.