The Library of Congress offers free Professional Development modules on their website in how to find and use Primary Source material in your classroom. Each module is worth one hour of Professional Development. When you finish each module, you can download a certificate to present as your proof of Professional Development.
Module One gives an overview of the Library of Congress and how to navigate it's sometimes tricky website.
Module Two gives some training in how to interpret old photos and prints with your class, using an Primary Source Analysis Tool - very much like a K/W/L chart, but adapted for a visual medium.
Module Three shows how to use the same tool to interpret antique maps.
Each module is interactive and was obviously developed by actual teachers who know how to get material across to other classroom teachers in an engaging way. In the course of finishing the modules, I found four or five new primary source documents to use in my Immigration Unit. These modules were so fascinating that I found myself chasing down several colleagues at school the next day and forcing them to watch clips from the modules. I'll be presenting the Primary Source Analysis Tool to our staff at a weekly staff meeting in a week or so.
(In proof-reading this post, I'm struck by the oddness of the fact that I can summarize a substantive Professional Development tool in just a paragraph or two, but it takes me a full page or more to talk about a Power Squid. I am, in the words of Buzz Lightyear, a sad, strange little man.)