Obsidian is a locally stored note-taking application with millions of PKM fans.
Joplin is an open-source note-taking application that is popular with developers.
Taskade is a project management software designed for small teams dosed with AI.
Amazing Marvin offers features to support organisation and reaching goals.
OmniFocus 4 is a place for busy professionals to manage tasks and sort projects.
Nirvana is a GTD focused to-do app to help to manage tasks and plan with GTD.
Getting Things Done Apps & Tools
Understanding GTD Apps More
GTD apps are very simply tools and apps that align with the concept of Getting Things Done by David Allen. The concept was developed in the 1990s by David Allen, but tools and apps can be adapted to it, to better align with your day-to-day GTD use.
GTD or Getting Things Done as a concept is free to consume. The book itself is priced between $7.99 and $14.99 depending where you buy it, David Allen's company "The David Allen Company" (the company behind it GTD) does offer courses and resources for free and paid workshops to help implement GTD within teams.
There are a range of task management apps you can use with GTD but tools like Evernote as a note-taking tool help you align to GTD too, it depends on what systems you tend to use day-to-day.
Second Brain and GTD work very well together, Second Brain is almost an extension of GTD and continue to help people. Here's a lot of Second Brain apps to explore.