OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Outlinely - Indispensable information organization tool for knowledge workers.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.