Goldmine user
I am a Goldmine user and a GTD'er as well. Like a lot of software out there, I know I am not using all of Goldmine's potential. However, it is a great fit with GTD. All of your pending activities are either Calls, Appointments, Next Actions, Events or Occasions. Within those given categories, you can code them even further...by context, for example. Then once you do that, you can customize all kinds of reports to print out and take with you if you are paper based, or sync with your handheld if you choose.
There are a few other Goldmine users on this forum...hopefully, they'll chime in as well. Just know that it is very powerful and very customizable.
Ryan