Below are a sampling of resources from the general web that include organizations devoted to advocacy, politics and policy, educational institutions, and think tanks.
Though these sources are recommended based on a certain level of credibility, you should approach any source with a critical eye. Ask yourself: can you trace the claims that are being made? Does that publisher have an agenda that may impact the content it publishes? If you are unsure about a source, act like a fact-checker: go outside the source and trace the claims, and learn more about author/publisher on wikipedia. When in doubt, or if you get stuck, reach out to a librarian or your teacher!
This is not an exhaustive list! Consider the nature of the topic you are researching, and how it might intersect with these organizations, or ones outside of this list. For additional organizations, visit the resources page of the Civil Rights Project out of UCLA or perform your own online search.
To vet a resource, keep the SIFT method in mind. Think like a fact-checker: can you verify or learn more about the organization by reading up on Wikipedia, newspaper articles, or sites providing an overview of charitable organizations?