Arc Notebook System - I'm a Fan!
In a nutshell, it replaces your regular binder with a proprietary ring system called the Arc. The big deal is that you can insert, remove, papers and accessories from your notebook with the security of a spiral bound but the flexibility of a 3 ring binder, with the panache fit for a boardroom meeting.
Video - if not showing is here.
Levenger has some same system (and as far as I know, the first) but is called the Circa system. The concept and rings are identical, with Levenger having a much larger selection but at a much higher price.
Apparently the technology was created by Rollabind - waaay back then. Check out Marth Stewart using the Rollabind system:
If you need these discs in bulk, rollabind.com is a great place to go.
Arc notebooks accessories and what I use.