Well, without jumping into a lengthy climatalogical debate, I'll add my two cents as to the original question.
One of my sites, Veg Porn, donates 5% of membership costs to different groups. I was surprised how hard it is to find animal-focused groups "willing" to take money from a porn site, so I gave up on the idea of vegetarian porn funding vegetarian projects. A few animal groups have emailed me, but they were either assholes to me (said that I better send them a lot of money if I wanted them to accept money from porn), wanted the money for something I considered dumb (buying scripts for their website), or I simply didn't like them. So fuck it, I'll give it to other people.
My store donates 5% of sales to Scarleteen, which is a very neat site, in case you aren't already linking to it. It's a great link to have on your warning page in hopes that young'uns will find some useful, honest, realistic, sex ed information:
http://www.scarleteen.com
Last year, the St. James Infirmary did a fundraising project with bay area strip clubs, which I also donated to.
http://www.stjamesinfirmary.org/ I think it's very cool to help fund services for folk other segments of the adult industry, especially the most at-risk people like street workers.
I don't do any regular thing with FurryGirl.com, but I've been meaning to think something up. I'm also trying to think of a good group to donate to from my upcoming menstrual site, but I haven't done much research as to the most appropriate group to the theme of the site.
If anyone is wondering about ROI here, I thought I'd add that I do get a lot of happy feedback from people who are glad to see adult sites supporting nonprofit groups. I'm sure it's helped win people over, and aside from doing something positive, I believe it is good for business to show that we smut-peddlers aren't all horny rich misanthropes. I think it would benefit everyone if the industry had more "giving back" projects. Most "special interest groups" and plenty of businesses do try to improve their image by doing something charitable, and it might serve us well to look at that model.