TaskBoard - A Kanban-inspired app for keeping track of things that need to get done.
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.
LeanKit by Planview - See how Planview LeanKit enables engineering teams across all levels of the organization with a visual work delivery tool to apply Lean management principles to their work, helping them work smarter and deliver faster.
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.
buckets.co - Feature rich kanban board collaboration platform.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.