Many LW readers choose to direct their charitable donations to SingInst with a view toward reducing existential risk. Others do not, whether because they feel they lack an understanding of the relevant issues, because they value present day humans more than future humans or because they have concern as to the incentive effects that would be created by donating to SingInst at present. I personally feel that there's a strong case for saving money to donate later on account of better information being available in the future.

However, I feel cognitive dissonance attached to saving to donate later rather than now. If you are in this camp you might consider donating to GiveWell's top ranked charities. Also note that spreading the word about GiveWell promotes a culture of effective philanthropy which is likely to have spin off effect of interesting people in x-risk reduction, reducing x-risk. 

See Holden's article on last minute donations http://blog.givewell.org/2011/12/30/last-minute-donations/ :

"Of the money moved to our top charities through our website in 2010, 25% was on December 31st alone. We know that lots of people will be looking to make last-minute donations.

If you only have five minutes but you want to take advantage of the thousands of hours of work we put into finding the best giving opportunities, consider giving to our top charities. They have strong track records, accomplish a lot of good per dollar spent, and have good concrete plans for how to use additional donations.

A couple of things to keep in mind:

• After you give, spread the word. This is the perfect time to remind people (via Facebook sharing, tweeting, etc.) to give before the year ends. And people making last-minute gifts are likely to be receptive to suggestions.
• If you have any questions, we’re here to help. We should be available by phone for most of the day, and responding to email when we’re not. (See our contact page). Our research FAQ may also be a good resource."