how do you create your video podcasts

Hi Gary,
I am still enjoy your podcasts and as a volunteer teacher in a non-English speaking country, I think it would be a great way to help my students if I could create short videos such as those you produce.
I particularly like the personal touch of having your image included while you talk through the instructions.
Can you tell me what software you use and how you get the images together.
As I am in a developing country, my budget is very limited, so if the software is expensive, is there an alternative.

— James Anthony