Boardly - A minimalistic planning board for your projects
Toby - Better Than Bookmarks
Corrello - Dashboards for agile teams using Trello
Weava - Workspace to highlight, organize & collaborate on your research articles.
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Kanban WIP for Trello - Multi Column WIP limits for Trello