I'm trying to gather together ideas on the use of physical calendars. Think erasable or disposable month planners visible in a living space or shared space like the family kitchen or office.

Does anyone use them as part of their GTD practice? How? What features must they have to be useful?

Do you see value in copying from digital to physical? What are the drawbacks?

Disclosure: I'm working on a design project to incorporate the best community ideas into a Creative-Commons-licensed month planner. A preliminary design exists but it's intended to be a continually evolving thing as well as offering tips and tricks about how to use it. I can't think of a better group to try and engage with.

Suggestions as to other influential forums with strong opinions on planning tools would also be gratefully received.