Rick Prelinger is an amazing individual to whom everyone with more than a passing interest in the less-traveled byways of culture owes an eternal debt, not only for being one of the first people to take ephemeral films seriously, but also for his subsequent work, of which just one example is founding the Prelinger Library.
Chief A/V Geek Skip Elsheimer periodically travels to various cities around the country to screen films from his massive collection. Like the DVDs he offers on his website, the screenings are usually themed - for example, a group of films dealing with alcohol and drug abuse, driving safety, or venereal disease (I believe he's writing a book about VD films, as it's a genre that's near and dear to him). I've had the very good fortune to catch quite a few of his screenings, as he paid an annual visit to a local microcinema for almost ten years. If you ever get a chance to attend one, they are not to be missed - he invariably precedes the main program with an educational filmstrip that involves audience participation and gets everyone in the mood for the films to follow.