not wanting to get too esoteric, but....for a while now i've been using todoist as my task manager. it's a great (& free) online service. what it's lacked, for me, has been an adequate iphone app. minttodo offered promise but doesn't really cut it. but any day now, doings should be in the app store - and it looks like it will finally bring all the benefits of todoist to the iphone.
i can't wait.
