I've found gtd and pomodoro to be a pretty perfect marriage. I've practiced GTD for 8 years now, and pomodoro for about 1. It works especially well since a lot of my NAs tend to be of the "write the introduction to article" variety, where there's really no smaller NA to break it into. The pomodoro technique helps with the "put your butt in the chair" aspect of those sort of NAs.