Org-mode is the reason I started using Emacs in the first place. I'd be hard pressed to come up with a more important tool in my productivity/organization tool

Org-mode is the reason I started using Emacs in the first place. I'd be hard pressed to come up with a more important tool in my productivity/organization toolbelt, it's become a really important part of my notetaking process. It's not perfect by any means (exporting to other formats in particular is kind of messy), but it's an insanely powerful platform that does a ton of stuff, and is just really flexible without being too overwhelming. At the end of the day, everything is just text, so you can get in really deep with scheduling and capture templates, or you can just write out nice TODO lists. Also check out Orgzly on Android if you're looking for a mobile client. Works pretty well with a Syncthing setup, or you can host your notes on a platform like Dropbox if you think that's easier.