What software software did MakeUseOf.tv use for creating podcasts before using google hangout on air? Or, how did you create this podcast http://goo.gl/wtr7WN?
So we used to use Google Plus for the live show, and we would each record locally. I would then go and edit the three video files together to produce the HD version. We've since switched over the Twitch, broadcasting through Skype and Open Broadcaster Software. It's a lot easier, and products a product that looks great, and is far less work in post production.
Check out the recent Twitch episode to see what I mean: http://www.twitch.tv/technophiliapodcast/c/5589899
But which tool you use to edit this podcasts to add images and illustrations.
Maybe it will help you to read the following article about OBS (scenes and sources).
In most cases videos are just queued up in a media player e.g. VLC or MPC on a second monitor and when you want to show them you switch to a 'scene' which contains the media players video as a 'source' and hit the play button. Same goes for YouTube videos in the browser, or images etc.
So for the most part, you plan those kind of things ahead, prepare them (mostly) on a second monitor and then show them on the fly during the podcast.
While James and/or Dave should be able to perfectly answer this question my guess would be Skype plus editing. At least that's one of the easy ways to do it for live streaming.
You create two monitor captures where the Skype videos are, arrange them as wanted and put an overlay image on top.