In the past few months, several of Nishio Sensei's video classes have been posted in their entirety on YouTube. Trying to absorb all the Sensei is teaching in these is a little like trying to drink from a fire hose, but I find his illustration of the links between weapon movements and taijutsu very enlightening. He also has a lot to say about the practical applications of the art and what makes aikido different from other Japanese budo.
http://www.youtube.com/user/NishioBudo
These are definitely worth a look.