Don't make me admit how, but I came across the Web site of the Ephemera Society of America a while back. I've been reading the articles from time to time, but haven't quite gotten around to sending in my membership fee.
I also poke around the Online Exhibitions page every now and then. It's really just a long list of links to the sites of other organizations or institutions that have created online exhibits from their collections.
I haven't checked out everything, but I liked looking at the Centennial Exhibition images— we did a lesson in one of our social studies books about it, complete with several illustrations of the equipment/inventions on display. The luggage label page is also fun. If my color printer wasn't on the blink, I might print some of those to use in some of my card-making projects.
Now playing on iTunes: Susan Tedeschi - Talking About