We get to talk to government and military people quite a bit, attending seminars and giving them presentations, and they nod wisely and ask pertinent questions which we answer. We're not sure how much this has translated into actual policy differences at the end of the day, but there does seem to be a class of people in government willing to listen to these ideas (informally, it seems that the military is more interested than the standard civil servants and politicians).
There are other policy achievements, but Nick and Anders would know more...
In case you didn't already know: The Future of Humanity Institute, one of the three organizations co-sponsoring LW, is a group within the University of Oxford's philosophy department that tackles important, large-scale problems for humanity like how to go about reducing existential risk.
I've been casually corresponding with the FHI in an effort to learn more about the different options available for purchasing existential risk reduction. Here's a summary of what I've learned from research fellow Stuart Armstrong and academic project manager Sean O'Heigeartaigh:
Although neither Stuart nor Sean mentions this, I assume that one reason individual donations can be especially valuable is if they free FHI researchers up from writing grant proposals so they can spend more time doing actual research.
Interesting comment by lukeprog describing the comparative advantages of SIAI and FHI.