For implementing GTD you can use this application:

Gtdagenda.com

You can use it to manage your goals, projects and tasks, set next actions and contexts, use checklists, and a calendar.
Syncs with Evernote and Google Calendar, and also comes with mobile version, and Android and iPhone apps.

This was a fascinating episode-- was kind of like listening to the "GTD Conversations" CDs that come with a GTD Connect subscription: views and processes of people outside my normal "tech bubble." Really enjoyed it.