Reddit is giving away 10% of their ad revenue to 10 charities that receive the most votes from the community. You can vote for as many charities as you want, with any account that has been created before 10AM PST today.
You can vote for your favorite charities here. I've had problems with the search by name, so if you don't find something, try searching by EIN instead.
You can also influence the votes by upvoting (and downvoting) your charities at /r/redditdonate. That is where discussions on the effectiveness take place.
As of this post, the placement is: GiveDirect-25, MIRI-47, CFAR-143, EvidenceAction-189, GiveWell-238.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.