Rebel Notes - Rebel aims to provide you a distraction-free note taking experience. Focus more on writing and less on formatting and saving. As you write your note, Rebel will format it based on your markdown syntax.
EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Notepin - Extremely simple note-taking + blogging ✍️
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.