None of these videos are mine but I found that they offer a lot of info for people just getting into casting and might be helpful.
two part mold basics
http://youtu.be/FQ1A7ZjTsx8
working with a pressure pot
http://youtu.be/hHIpGewFhnY
working with vaccum & pressure
http://youtu.be/XMdicfz5Ouk
A longer mold making tutorial (8 parts)
http://youtu.be/jFfXT_Cjpuk