Oyate is "a Native organization working to see that our lives and histories are portrayed honestly, and so that all people will know our stories belong to us," and has a ton of useful information on its website. They are currently raising money toward a matching grant to revamp their website, and they need to meet their goal by this Saturday, August 1. They're very close, so any donation will help: please check them out.
ETA August 1: money raised! Thank you all!