Some causes where a little goes a long way (plus career advice in first link):
https://en.wikipedia.org/wiki/Effective_altruism#Organizations
https://www.thelifeyoucansave.org/impact-calculator

Useful browser extensions:
https://chrome.google.com/webstore/detail/tab-for-a-cause/gibkoahgjfhphbmeiphbcnhehbfdlcgo?hl=en
https://chrome.google.com/webstore/detail/ratings-preview-for-youtu/cgbhdenfmgbagncdmgbholejjpmmiank?hl=en

If you like to learn a lot of stuff:
http://slatestarcodex.com/blog_images/ramap.html
https://cse.google.com/