Well, if we're talking what I personally would do, I would donate that money to an arts association or a library or similar. The national ballet, a university library, a non-income-based merit scholarship at my old school, etc.

But this is Improbable Island. We are From the Internet. As such:
Something apolitical, something worldwide, something that is not religious. Something that spends most of its donation money actually helping people, rather than funding the organization's mini-bureaucracy.
I can't really add any charity name that hasn't already been said. But these are my criteria: if the organization fits these criteria, I'd probably support the donation wholeheartedly.

Looking through what everyone else has said, I'm tossing my opinion towards ASPCA, 826 Valencia (a new discovery for me, wow) and were it me personally? I'd throw some of that towards American Rivers and First Book. Probably split it 25% each way.

two choices for me, first would be ASPCA (animals play a big part in our lives, even if some people dont see it)
and.. the Cancer Research Foundation (i dont think i really need to explain this one) atleast thats what i would donate to, probably 50/50

I'd donate to a single organization - mainly because bureaucracy would take up less of the total amount in that case.

I'd have suggested AVERT.org (AIDS prevention and treatment mainly in Africa and India, for the same reasons as Paul Lo) and the newTree.ch project (planting trees/green belts to keep deserts from spreading, improve soil, and create/protect a habitat in the endangered Sahelian zone, my school's supporting it as well), but neither of them seems to support PayPal... (Not that I am particularily fond of PayPal to begin with.)

Lots of suggestions so far. We don't really need any more, unless anyone has something that's particularly close to their heart that they'd like to add. What we really need to know now is - Which charities accept Paypal. That seems to be the limiting factor. CMJ, some alternatives to Paypal have been suggested. Are any of these feasable?

Next, how efficient are these charities? Spending 65% of your income on fund raising doesn't seem particularly effective to me, even if I can understand why they do it. Their primary concern is the cause they're working towards, not giving the likes of us a warm fluffy feeling. If devoting 65% towards fundraising ultimately gives you more money for the cause, then that's the best thing to do.
In the end however it comes down to charities fighting each other for funds. I know some people who work as chuggers and they all say that it's a serious jungle, and can get quite vicious. They might be increasing their share of the pot, but the total pot is more or less fixed, and overall, less money is getting spent on the various causes. Hence I believe in supporting efficient charities.

My personal list of priorities would be :-

1) Childrens charities. Especially charities that combat child abuse. Kids are our future. If they're getting abused then that leads to more problems in the future. Shit breeds shit breeds shit breeds shit. Kids who've never been shown any respect never learn to respect anyone or anything else. Sort that out, and I think you're nipping a lot of future problems in the bud, especially things like animal welfare for example, but also all the many problems caused by mans inhumanity to man, and they form a significant chunk of the worlds problems. Of course there's always the immediate concrete 'This person is being severly harmed. We can do something to stop it.' moral imperative as well.

2) Environmental charities. The planet as we know it is going to hell in a handcart. If we're not careful then there's a real chance that we'll face a situation which makes the EMP which hit the world II is set in, look like a walk in the park. If civilization as we know it goes down the Swannie, then most of our other problems will just not be problems anymore, in a bad way. Cancer for example will be competeing against so many other painful exotic and nasty ways to die that it just won't seem that much of a problem.

3) Third world poverty charities. Reasons similar to 1) on a larger scale. Also I think that most of what these charities are trying to do is just basic morals. It won't make any of us a great saint, just stop us being great sinners.

4) Animal welfare charities. This is my fluffy side coming out. I like animals. Also basic morals, as in 3).

I'd also prefer some sort of global charity. Whilst schools in New York, for example, is a very worth while cause, I tend to empathise more with British charities for the entirely subjective reason that I'm a Brit myself. Presumably Americans are more likely to empathise with American charities, the French with French charities and so on. Something that we can all empathise with equally would be good.

So far 'Medicins Sans Frontieres' gets my vote, although did someone say they didn't take PayPal? That would be a pity.

I don't know many charities, but I'd go with-
Cancer/Aids research-50%
Feeding hungry folks-25%
Human Rights (darfur, amnesty Int.)-25%

Also, would have to be a group with no political agenda, who uses the lion's share of the donations for the work itself.

I personally would like to donate a bit of money to Child's Play, mainly because I admire when games are used for good things, like brightening up a child's life. Another organization I'd consider would be the American Cancer Society.

Personally, I'd go with the one I run, Lost Dimension Games. Probably not a good choice for II, though, because (a) you don't know me, and we haven't accomplished much visible yet, so it's not obvious that the money would be used well, and (b) we're not 501(c)(3) yet, so it's not tax-deductible and arguably doesn't count as a "charity" despite being non-profit.

For II, I'd recommend EFF. They do a lot of great work. If you're not familiar with them, think of them as the "digital ACLU".

I somehow feel that MSF is the most appropriate choice for Improbable Island, but I just checked and they have donation pages (for MSF and doctors without borders, same story) that only accept cards. Now, I don't know much about paypal, but I do know it is possible to get a paypal debit card.

https://www.paypal.com/cgi-bin/webscr?cmd=xpt/Marketing/account/DCIntro-outside

There's a $3,000/day spending limit, isn't that funny? Maybe you could get around that by calling paypal? I don't know, I try to avoid talking to the credit card companies whenever possible.

I know it's already been said, and I don't know if there's really a chance to contribute anymore, but my feelings are towards Doctors without Borders. I respect what they do to an incredible degree.

It takes so much dedication to help people in areas of conflict, where your own life is at risk.

Another organization (i don't know if they count as a charity or if it's been mentioned) is Kiva.

Borrowed from Wikipedia: "Kiva Microfunds is an organization that allows people to lend money via the Internet to microfinance institutions in developing countries around the world and in the United States, which in turn lend the money to small businesses"

I've had no experience with them, but it seems like a good idea.

I vote for St. Jude's, as to my knowledge they run entirely on donations, and give free medical help to those in need.
http://www.stjude.org/stjude/v/index.jsp?vgnextoid=f2bfab46cb118010VgnVCM1000000e2015acRCRD


If not, maybe Red Cross.
http://www.redcross.org/

I really don't have any detailed reasons to give, I'm afraid.

This is a difficult question to answer. I did a little bit of poking around online to look at options before I settled on Children's Cancer Center and American Wildlife Foundation.

I like kids and I like animals, so I was drawn to these groups. Both of these organizations are highly-rated. I would split the money two ways and give equal portions to both of these groups.

I like heifer international, they give animals to people in developing countries. If you get an animal from them and can breed it you have to give some to your neighbors too, so one gift can have a large impact after a while.

http://www.heifer.org/

The PayPal requirement knocks out several of my favorite charities from the get-go, unfortunately. Right now, if I didn't have time to do some more research about who does and doesn't take PayPal, I would say split the $10,000 evenly between the following two organizations:

Kiva Microloans
http://www.kiva.org/

Rape, Abuse & Incenst National Network (RAINN)
http://www.rainn.org/

The benefit of this is that the money paid to Kiva would be repaid to you so that you could continue to reinvest it in impoverished nations again and again, or if you'd rather, you could invest once in Kiva and then take the money once you are repaid and donate it to a third charity. It's almost like being able to give 50% more money than you actually have.

The American Cancer Society.
Cancer has claimed several of my loved ones. For a cure to be found is one of my hopes.

Plan International. Or a deserving cancer charity, i.e. not one of the research ones, but one of the ones on the front line, offering support.

I really love the whole World Community Grid idea, so I would probably do the following: I would buy a PC (or a Mac ;p ) for a bit over 9000 (pun intended) with as much CPU-power as possible (and as little anything else as possible) and use it to run the BOINC client 24/7 (the remaining <1k$ would go for its electricity bills ;p )

I would have to say split it between ASPCA, AIDS research and treatment, and cancer research. Though I can't recall off hand any charities that take paypal.

Amnesty International, every time. The work they do is, in my opinion, amongst the most important there is - they state their mission as:

Just a quick pointer: That last one? That were me. Also, I'd like to point out that Amnesty are about as humanitarian as it gets, are particularly supportive of children, for obvious reasons, and are entirely nonpolitical.