Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Pocket Lists - World’s Friendliest To-Do List App
Nifty - Manage projects, work, and communications in one place.
UpNote - A beautiful and clean cross-platform app for notes organizer
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Synology Note Station - Without needing to spend money on Evernote, Synology Note Station provides a desktop client to organize all your random notes in one place.