I've made roughly 900 videos in Norwegian, in the same style as Khan Academy over at http://udl.no - Check out the videos and see if it's what you're looking for.
I use SmoothDraw3 to draw into.
I use a Wacom tablet to draw on. Most Wacoms are affordable, and surprisingly good quality. I've had the same one for over 3 years, and not a single thing has changed about it.
I use Camtasia Studio for recording and editing, though very little editing is required.
I use Geogebra for visualizing graphs to prove calculated tendencies and critical points, and what-have-you.
I use Casio FX9750 software for on-screen calculating, but only when it's needed. I limit my use of proprietary software in case I decide to run ads on the videos. Most of the time, I only use the Windows calculator as it has more functions than most people know about.
Other than that, feel free to ask if I've left something out.