Todo.sh (bash script to manage a text file) is quite nice. See screencast here - http://www.todotxt.com/library/todo.sh/
I have to agree with this comment. I've been using todo.sh as well and it works wonderfully. It's easily parsed, there is a community working on making it better. And there is even an initial port to Python as well.
I'm using a similar command line tool for managing my todo items: http://swapoff.org/DevTodo# Jan-Wijbrand Kolman