I have a large notepad on my wall I use to make mindmaps all the time. I also use it to plan out businesses, as well as about everything else.

I'm thinking about getting one of those large dry erase boards that Yanik and John Reese use. (custom built to your size).

Of course if you really want to go all out... have your walls painted in the dry erase stuff like John Reese's war room. One day I'll have that done.