My goal is to make a powerpoint show in which a figure walks around on the slide. I think I can accomplish this by rendering an image sequence in .png format, then combining them into a video that preserves the alpha channel transparency, and insert the video onto the powerpoint slice. What might be the best video format to do this in, and what is a (not exorbitant) application that can do that conversion? Thanks

Sorry to see you have not gotten a reply yet. I don't do animation so cannot help but suggest you try asking your question in the Blender forum.

Sorry for the delay - Hitfilm (Free version but you can add modules at reasonable price right up to importing 3D models) Not sure what OS you are on but something like Simple Video Converter would come in handy (free version in windows store).

You could use animated gif if it is not a long sequence. You really do need to say what OS you are using, otherwise most people will assume windows. I mentioned virtualdub in your thread in the other forum. There are not many formats that keep the alpha. Can you use flash?