Paulu posted me this plea made by another organization. I second that it sounds like a good idea.
The human rights organization Domestic prisoners of conscience has sent out a plea for us to write a simple letter every month.
Letter write day every 26th of the month
They believe that a simple letter of comfort can benefit those who are sent away without any access to legal aid or court process.
I find that it is a good initiative and supports the idea. I have adopted a certain person I will write a letter every month until this person is released.