Here are a couple videos I consider worth watching. The first one is of Mifune Kyuzo (or Mifune Judan as he was known). I spent $50 on the DVD of this footage, but here it is for free
on the internet. There's so much to see here I don't know where to start.
Second is the only footage I have seen of Tomiki Sensei. Very intersting stuff from an often overlooked part of Aikido's history. Click here.