These are so cool: US bread wrappers of the 40s and 50s. Besides being tons of fun, the pictures are good enough to print out if you need to make period wrapped bread. Incidentally, the site this is from, How to be a Retronaut, is chock-full of the most wonderful vintage and historical pictures. You can waste hours of time on this site while rationalizing that you are “doing research.”
I’ve pointed to the Early Office Museum site before, but I just found this gallery of Really Big Stuff. It’s photographs of early office equipment, like typewriters and rubber stamps, constructed at large scales (think “parade float” size). It’s also a good opportunity to check out the site if you haven’t heard of it before.
The NIOSH Pocket Guide to Chemical Hazards is an extremely useful source of information for the hundreds of chemicals listed as “hazardous” by OSHA and found in the stuff we build props out of. Rather than serve as an exhaustive guide to all information, it lists key information about each chemical relevant to work. You can view it online or download the whole thing as a PDF; I’m also throwing the link up in the sidebar of this site so you can find it every time you visit.
The Historic Naval Ships Association has a 1949 training manual titled Engine Room Tools presented in full on their website. It illustrates and describes the tools one would find on a ship at the time, namely metal-working hand tools. They are surprisingly similar to the metal-working tools you would find in a props shop, and the illustrations demonstrating their use are very cool.