I guess you did not know that good old IBM Notes also is a GTD-tool and not only an email client. And the most surprising is that the inventor and founder of the GTD method, David Allen, uses IBM Notes in his company – with an overlay named eProductivity that makes IBM Notes into a GTD tool.
As a matter of fact, I used to have that overlay on my IBM Notes client too. Back in my first years as a Lotus Notes sales rep at IBM. I found it very useful, though a bit complex to use.
But, like IBM Notes, it’s still running out there among enthusiasts and also on David Allen’s desktop!
Here is the video where David tell about the apps he uses to Get Things Done: