I recently stumbled on asciinema, which is a way of screencasting execution of code on the command line. Since the file format is apparently a JSON file, the storage and transmission requirements of the screencap are fairly minimal. Moreover, as one is watching playback, one can pause and copy and select text from the screencap. I feel like this is an amazing technology which has been missing all my life, but to be honest I am not sure how I should use it yet. For now, I am playing the recursive gambit of screen-capping the writing and publication of this blog post.
Here's the embed: