L'Officiel de la Mode n°563-564 de 1969.
L'Officiel, the French luxury magazine responsible for launching the careers of Christian Dior and Yves St. Laurent (among many, many others), now has an online archive of every single issue from 1921 - 2008. The archive includes each issue scanned in it's entirety -- advertisements and all -- and features a sophisticated search engine (want to see every Dior ad from 1947?).
Spread from L'Officiel de la Mode n°301 de 1947.
Aside from the obvious fashion interest, it is a stunning visual archive of photography, illustration and design. A real treat from one of the longest (perhaps the longest, anybody know?) continuously published fashion magazines in the world. Though the website is in French, most of the navigation is via thumbnails. (tip: click "PLEIN ECRAN" to launch the full-screen viewer.)
This is exactly the sort of thing that I'm excited, and expecting, to see a lot more of over the next few years.
UPDATE: The lovely Ms. Sarah Bradley has just informed me that Harper's Bazar (now spelled Bazaar) has been in publication since 1867! We can only hope they'll follow suit and make some of their own history accessible online.