I use org mode in emacs to take notes from web browsing and to store notes about projects I'm working on. It's plain text but allows for hierarchical organization, tags, generation of spread-sheet like tables, etc. and I can always export it later to something that non-emacs users can look at, like html or pdf. Being emacs, there is an absurd amount of stuff that can be done with the document, including the ability to compile and execute code snippets in the languages that I use (I am a programmer, so this is sometimes quite helpful).