There isn't much mention of mopeds in this exhibit, but some of you might of seen the Art of the Motorcycle when it was in museums around the nation over the last couple of years -- I saw it in Chicago. The Guggenhiem has now created an awesome online presentation with all the information.
It has high-res photos, Quicktime VR for each bike, audio tours about the history of each bike, and more that I didn't have time (I'm at work) to check out. If you have a cable or DSL modem definetly chose the high bandwidth version.
If you're wondering about moped content, they do profile the Solex Velosolex. There is a history of the company and they mention that Motobecane took over production in 1974.