Cronofy - Unified Calendar API for developers
TideTask - Control your procrastination and never miss a task again
Calendarix - Calendarix is a powerful and easy to use web-based calendar that runs on PHP and MySQL.
Motion Firefox - All-in-one time management tool in Firefox
Campaign Calendar - Campaign Calendar by Bracket Labs builds a marketing calendar from your Salesforce Campaigns.
Taskable - Using multiple work apps leads to tons of context switching, breaking flow and killing productivity.