I have been using Trello to keep my different lists organized: Inbox, Today, This Week, Waiting For, and Done. Then I use labels to determine priority: Important, Not Important, Urgent and Not Urgent.

Here is a great article by Gautam Ramdurai, who works at Google on how to incorporate Trello with your GTD workflow: https://medium.com/precise-curiosity/locus-focus-an-approach...