Lightboard
I build a lightboard at home last summer in order to give my classes (this was inspired by Ivo Vekemans - here's an example of him lecturing). I recorded three whole classes so far, and a bunch of seminar talks. Here's a talk of mine. Overall, I'm very happy with the setup.
Advantage: The result is really beautiful to watch.
Disadvantages: The lightboard + recording equipment uses up a whole room in my house. Also, it's a bit time-consuming to clean the board (if you don't clean it well, it leaves lots of shiny smudges). This makes it essentially impossible to give live talks on it.
This youtube video discussescompares two different types of markers for lightboards, including how they erase. (Btw, to erase, just use a dry cotton cloth – certainly no window-cleaning products.)