Not talking PIMs or PDAs here, but attempts at organizing thoughts, documents, email, etc. to varying degrees. Brad DeLong links to a long list of software for the Mac that tries to meet the task. I’ve used DEVONThink and am going to give it a go again to see if it helps (I’ve found some cool scripts and might work on more to see how well it can deal with different tasks). I also have OmniOutliner which is really not even in the same class… good for taking notes at conferences or meetings, bad at the other things that DEVONThink or Boswell try to do.