[tedmiston]

That sounds like the Levenger Circa system. I never tried them myself (thought they were too pricy), but they are popular in the GTD crowd.

http://www.levenger.com/circa-notebooks-339.aspx

I did Hipster PDA for a while, which you could kind of consider a poor man's version.

http://www.43folders.com/2004/09/03/introducing-the-hipster-...

[Jtsummers]

The Circa notebooks were my introduction to the concept. Arc is cheaper by a good bit. The rings are slightly different but paper from one will work on the other, maybe not perfectly but functionally.