Update: You can lock your list with your password by 1 click now.
You may have used other Todo list applications thus far. But now, whether you can decide which Todo application to use or not, you have to use Thingler at least once. Thingler is an oh-so-pleasant open source web-based Todo list application, and was built with node.js in JavaScript.
Thingler depends on server-side JavaScript using node.js
