Hi Betsy,
I do a lot of online video tutorials using a combination of Keynote, Quicktime, Mouseposé and Vimeo.
Keynote - is useful to create a written introduction that can be emailed to the person you are training. (Also can embed Vimeo links)
Quicktime - allows you to record your screen - and you can capture voice nicely using an external microphone
Mouseposé - this useful app allows mac users to highlight the position of the mouse cursor. Good if you're trying to allow someone to follow your movements.
Vimeo - password protect your videos and upload them
Hope this helps,