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.
Cvent - Cvent's event management software provides event planners with a complete solution to increase event attendance and decrease event costs.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
EventMobi - EventMobi is an interactive mobile event app, audience response and engagement platform for conferences and trade shows.
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!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets