I'm amazed that noone has posted a link yet to the Existential Risk Reduction Career Network. Or maybe someone did and I haven't noticed.

Here's the description on the site's front page:

This network is for anyone interested in donating substantial amounts (relative to income) to non-profit organizations focused on the reduction of existential risk, such as SIAI, FHI, and the Lifeboat Foundation. For more information on existential risk, please see Nick Bostrom's original paper, or Wikipedia for a brief overview. We are a community of people assisting each other to increase our resources available for contribution. Members discuss the strengths and weaknesses of different careers, network, share advice on job applications and career advancement, assist others with finding interviews, and occasionally look for qualified individuals to hire from within the network. If you are interested in joining us, please see our page on requesting invitations for more information.