there is no spare time, as you surely know. any time spent on this comes out of study time, personal time or family time; from preparing the quiz cases to slides and discussion material to the final product the whole things takes about 12-15 hours for me, spent once a month over 1-2 weekends. I just hope I can keep at it, as exam time is coming up. It is a joy for me though, and I learn a lot myself in the process, which is fun! Hopefully in time I find other radiologists/residents who are interested in submitting quizzes, and that will make things a bit easier.
as for the software, I do it all on a Mac. I prepare the slides on Keynote, export them as images, them import them into iMovie as stills. I then record the narration in Garageband, import the file into iMovie and then adjust the slides to the voice. It can alternatively be done with direct voice over on slides, in powerpoint, keynote or even via software such as Camtasia; however, I am still not a good speaker and usually do a bit of sound editing to make the narration better, so I do it in a music editor such as Garageband. Once my lecture skills improve, I may try direct voice over to save some time.