There's a missing be-all, do-all, external brain app that I've always wanted in this space. Something that aggregates data from the internet offline; something that stores all my projects and info; something that stores tasks in a useful format; something that exposes lenses on that data (calendars, task lists, mind maps); something that ties into my browser to let me store new things and find existing things (imagine if your awesome-bar searched your external brain before heading off to Google!); something that bookmarks things; something that stores all my notes. There've been a few attempts at the be-all/end-all PIM, but nothing's achieved enough of it to stick, IMHO.

In the meantime, for daily stuff I slap things into a text file in Sublime Text, for longer term stuff I schedule things into my calendar so that I'll remember to slap it into the textfile for the day on the day. I've tried so many TODO managers, paper notebooks, etc. -- nothing seems to stick, because I always get frustrated at how small the scope is and tack things on the side until the house of cards collapses.