Pen and paper. It's the most flexible, and least intrusive way to take notes while still participating in the meeting. Sure, I spend 5-10 minutes afterwards or that night copying the notes into my CRM or task manager, but the benefits far outweigh the extra time for me.
+1 for OneNote. It's surprisingly unknown for a great product. And also integrates easily to outlook if your using this.
One thing if people want to use this spend the time mapping out how you want to organise your digital notes. OneNote runs on three tab layers (plus in page) so its worth deciding a structure to co-ordinate how you will organise before you start using too much.