For the last 10 years I've really been obsessed with improving my own productivity, and after all the fads and gimmicks, my ultimate conclusion is that the keys to productivity are discipline and focus. I feel like anything more complicated than a simple list just adds to overhead, and ends up eating into my time more than it streamlines anything (incidentally I sort of feel this way about Twitter too, so you're in good startup company). I'm a real big fan of a pocket moleskine for keeping todo lists, jotting down ideas, and just generally dumping stuff into any time anywhere. I find I never have a shortage of things to do (especially now as a new father), so the problem isn't being able to track them over time or see them all at once. It's just about immediate priorities which should be decided quickly and decisively. If something important gets missed, it will make itself known soon enough.