Eagerly awaiting that "Calcurse/todo.txt" howto I see on your To Do list
I'm still working out the details. I figured out you can get todo.txt and calcurse to use the same todo file which makes adding and marking todo list items easy from command line, text editor or within calcurse. The only problem is that if you have autosave set in calcurse it will overwrite the todo list if you have modified it via todo.txt and not reloaded the file in calcurse.
I've moved this thread to Tips and Tricks as I'm looking for input from other users of these two very useful terminal apps.
Calcurse is a text-based calendar and scheduling application, it uses flat, human readable files for holding data about your calendar, appointments, and todo list.
Todo.txt is a simple and extensible shell script for managing your todo.txt file. With a couple changes to todo.txt's config file you can set it to write the ~/.calcurse/todo file giving you the ability, after adding a bash alias, to issue a command like
Add items to your todo list in Calcurse
t add buy groceries
Quicky mark and item done and archvie it, making it invisible to the todo list but still kept as a list of completed actions.
t do 2
2 refers to the line number in the todo file.
When adding or editing todo items in Calcurse you can assign priorities  being the most important  being the least.
For me, with the inclusion of Mutt for email provides a complete solution for productivity, including human readable text files and the ability, if you run conky, to have your appointments and todo list on your desktop. See this link for screenshots of my todo list.
if you use either of these apps or just like the ideas of a cli approach to getting things done please share your ideas on ways to integrate the two further. I'm currently working on a howto for the setup.
I wrote the author of Calcurse posing three questions I had before writing my howto.
1. Is there a way to have calcurse append to the todo file rather than overwrite it?
2. Is there a way to add/delete an item to the calcurse todo list via command line?
3. Is there a way to have calcurse reload it's config files, without saving to them first?
Regarding your questions, unfortunately I must answer no to all of the 3 questions...
So it looks like the current functionality is the extent of the functionality for now, making any further HowTo tough until one of the three things comes about. He did mention that a couple of command line flags would be a good thing, and possibly implemented in the next release. Unfortunately he is unable to give any sort of idea of when that might be due to his schedule.
As posted on my blog.