I just had a former intern ask me for advice on finding jobs in the DC region in international affairs. I compiled a list for her and thought it might help others. Here it is.
A good first choice is searching/following the websites of individual companies that you would love to work for. Research the companies, then keep checking. Even if they don’t have anything immediately available that suits you, you’ll still get a better sense of what they do, who they want, and what projects they’re working on. When a spot opens up that even remotely interests you, you’ll then have the background knowledge to integrate into your cover letter and (hopefully!) interview.
I’ve found my university career website to be quite good. Check it regularly.
A few other options: