https://www.reddit.com/donate?organization=208096820 [Tor Project]
https://www.reddit.com/donate?organization=592751953 [MAPS]
https://www.reddit.com/donate?organization=203256212 [Erowid]
You can also go here and search for charities to vote for yourself, you can vote for as many as you want.
From comments:
http://www.reddit.com/donate?organization=43091431 [Electronic Frontier Foundation]
I won't be stickying this (as today is Wednesday) so if you think this kind of thing is cool remember to upvote so it doesn't get buried.