Paws for Trello - The best way to use Trello on your desktop
Hello Epics for Trello - Simplify your Trello board with parent/child relationships
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
TunnelVision - See your next Trello tasks every time you open a browser tab
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
StandupScreen for Trello - Turn a magnetic whiteboard into an interactive Trello board