One thing fans of the GTD ethic like is a to-do list manager that doesn't get in the way of the good work habits you're trying to create. Nexty, an open-source webapp created with GTD principles in mind, fits that bill.
Nexty is a terrific little tool for arranging your to-do lists by project and easily cross-referncing them by context. You can check all your tasks, figure out your Next Action, set reminders, and see due dates all in a few clicks. Nexty comes with pretty much all the bells and whistles you'd expect to see in a GTD webapp, and was obviously written by someone familiar with David Allen's Getting Things Done system.
Nexty is free to use, and site registration is quick and painless. If you want to host Nexty on your own server, knock yourself out — the open source codebase is available for anyone who wants to take or improve it.