They are an organization fighting for the US right to be out and about without a ID.
They have a project you can help them with. According to the Gilmore case, when you fly in the US, you don't actually have to show ID as long as you submit to "secondary screening". So the Identity Porject is encouraging people to refuse to show ID when they fly, and to report back to them on the experience:
I don't think I'll be doing it as I can barely stand to be in airports at all, but...