Despite my net worth being in the negative five figures, I still try to donate to organizations I support, and (while doing my taxes for 2012) I had occasion to make a list of them. These are not the only organizations I've supported, but they are my favorites. Here they are, in case you have more money than you know what to do with and want suggestions.
ScarleteenI wish I'd had access to this site when I was 12 or 13. (I still thought that "oral sex" referred to kissing at that point.) In a country where whether teenagers should get accurate information about sex in school is a controversial subject, sites like this are sorely needed. Scarleteen is a labor of love by Heather Corinna, whose online presence I've been following for a while now, and her commitment and dedication to maintaining the site for minimal reward is inspiring.
The Ada InitiativeOpen-source and free software communities, as well as free culture projects like Wikipedia, continue to be hostile environments for women, people in gender, sexual and romantic minorities, and lots of other people who are from groups that have outsider status. It doesn't have to be that way, and it would be better for everyone if everyone who had desire and energy to contribute was able to participate in building the future without fear of humiliation. The Ada Initiative is the only group I know of that is specifically working to make that vision a reality. I have had the pleasure of meeting and interacting online with both of the founders, Mary Gardiner and Valerie Aurora, so I have particular confidence in TAI's effectiveness.
National Network of Abortion FundsIncredibly, getting an abortion in the US in 2013 is still highly dependent on one's income, and we still are a nation where being forced to give birth to a baby because of inability to pay around $500 (or in many locations, thousands of dollars when travel costs are factored in) is far from unheard of. The National Network of Abortion Funds focuses specifically on funding abortions for people who can't afford them, as well as changing unjust laws like the Hyde Amendment. They are sometimes good (not perfect!) at using language in their publicity that acknowledges that people who get pregnant and need abortions aren't always women. Stacey Burns, the online communications manager for NNAF, friended me on Facebook after I did a Causes.com birthday wish for NNAF a few years back, and through reading her posts, I've gotten a good sense for the kind of activism that NNAF represents, and that it's something I want to support.
All Hands VolunteersIn the summer of 2010, I went to Léogâne, Haiti for six weeks to help with earthquake relief. All Hands Volunteers was the group I volunteered with. I ended up leaving Haiti after four weeks instead of six -- turns out heavy labor in extreme heat wasn't the thing I was best at (and after years and years of sitting at a desk 40+ hours a week -- who'd have guessed?) While I was there, though, I saw firsthand that All Hands is a group that's very effective at getting a lot of work done with a small group of very committed volunteers. Since then, they've initiated disaster relief projects in the Philippines as well as post-Sandy relief in Staten Island and Long Island. Some of the volunteers I met while working with All Hands were among the most inspiring people I've ever met.
Lyon-Martin Health ServicesI'm biased -- Lyon-Martin, in San Francisco, is where I get my primary health care. It's a place where I can feel confident that I won't be treated awkwardly or be forced to educate about being a man with a transsexual body, and it's also a place where trans women, queer cis women, and genderqueer people can feel confident of the same. They operate on a shoestring and were close to shutting down not long ago. You should give not just if you want to support respectful health care in the Bay Area, but also if you want to make sure that the informed-consent model for trans health care spreads further.
Partners in HealthYears ago, I read _Mountains Beyond Mountains_ by Tracy Kidder (on the recommendation of a LiveJournal friend!), a biography of Paul Farmer -- who, along with Ophelia Dahl, founded Partners in Health -- and it has affected my thoughts, if not yet my actions, ever since. Paul Farmer's belief in and work towards providing the same health care to poor people that (say) a Silicon Valley software engineer like me would expect for themself or for their friends and family is challenging and is a source of hope. I also appreciate that while PIH is non-sectarian, it's inspired by liberation theology; _Mountains Beyond Mountains_ quotes Farmer as saying that he knew there had to be something to religion, because rich people hated it and poor people derived strength from it. I like that. And PIH gets stuff done (plus, Ophelia Dahl graduated from my alma mater, Wellesley, reminding me that not everyone from my school becomes an investment banker).
Transgender, Gender-Variant and Intersex Justice ProjectThere are big-name organizations that call themselves "LGBT" when the "T" really stands for transmisogyny and the B is silent, but the TGI Justice Project is the real thing. Just as PIH focuses on providing health care where it's needed the most, TGIJP focuses on the needs of that subset of the "LGBTIQ" cohort who need justice the most: trans women of color who are or have been incarcerated or who are targeted by the criminal justice system.
Having written this list, now I'm looking forward to having my debts paid off so I can support all of these organizations more thoroughly! If you particularly want to support organizations whose work is of a global nature, Partners in Health and All Hands Volunteers are your best bets on this list. Most of my favorites are US-centric, though, since I believe in helping with the needs that I'm most familiar with (since who else is going to but the people who are affected?)