Lunyr - A decentralized crowdsourced encyclopedia.
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.
Tealfeed - A knowledge sharing platform to empower creators
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!
Noat Cards - A knowledge learning and sharing platform
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.