The most obvious is of course the clothes themselves, so much inspiration has started to come out of these in terms of design, but also other things I hadn't really thought about. One thing that has struck a surprising cord is the models themselves! The styling of course is great, but also the poses! Models stand a different way in a lot of the garments because the clothes themselves took a subtly different carriage to show off the designs, full skirts, curves and general feel of the time all shop up in different ways on the models.
Web DesignI love reading the copy on a lot of the items too, you can get a great idea of what was important to each catalogs demographic from the way each product is described. Add onto that the layout, typography and graphics which are so great, and these have played a large part in my latest site re-design! One of the main reasons I picked up my first catalog was to help with the shop re-design and to hopefully make internet shopping as retro friendly as possible.
Home Decorating (not work but...)
I know a lot of folks out there like to indulge in some retrofication of the old homestead too. I've probably spent hours going through the home sections of the bigger catalogs for furniture/decor inspiration, it's just a shame we can't just pick up the phone and order those awesome curtains!
Good for Giggles
It's true too that not everything old is cool, I got a few giggles out of some of the photos/products that time has just not been kind to, things for example like the faux fur hat that doubles as a wig
I'll admit that some of them have a fusty "I've been in an attic for 50 years" smell that is less than fun on the allergy front. but adding some primary sources to my "library of awesome" is possibly worth a sore throat or two.
For an easier peek inside the world of flea market catalogs there are a few collected books out there that do just that from Amazon