GanttProject is a cross-platform desktop tool for project scheduling and management. It runs on Windows, Linux and MacOSX. (GPL)
Cross-platform
Jobsworth can be used for helpdesk support ticketing, customer liasion, resource management (eg. systems and password tracking) and has a range of CRM type functionality. Plan your projects, see your schedule, know if you're slipping behind and why (AGPL)
Cross-platform
With Jorani you can deploy a workflow for the leave and overtime requests of your organization. When creating en employe, specify its line manager and this manager will receive by e-mail the leave and overtime requests of its collaborators. (GPL)
Cross-platform
LibrePlan is a collaborative tool to plan, monitor and control projects and has a rich web interface which provides a desktop alike user experience. All the team members can take part in the planning and this makes possible to have a real-time planning. (AGPL)
Linux
OpenProject is a web-based project management system for location-independent team collaboration. Open source project management software. Powerful. Easy-to-use. Free. (GPL)
Cross-platform
Plan is a project management application. It is intended for managing moderately large projects with multiple resources. (LGPL)
Linux - FreeBSD
Project-open is a web-based "Enterprise Project Management" software for project-based organizations with 2-200 users. Project-open integrates areas such as CRM, sales, project planning and tracking, collaboration, invoicing and payments. (GPL)
Cross-platform
ProjectLibre desktop is a free and open-source project management software system intended ultimately as a standalone replacement for Microsoft Project. ProjectLibre has been downloaded 5,500,000 times in 200 countries on all 7 continents and translated into 29 languages. (CPAL)
Cross-platform
qdPM is a free web-based project management tool suitable for a small team working on multiple projects. You can easy manage Projects, Tasks and People. Customers interact using a Ticket System that is integrated into Task management. (GPL)
Cross-platform
Redmine is a flexible project management web application. Written using Ruby on Rails framework, it is cross-platform and cross-database. (GPL)
Cross-platform
SoFreakingBoring is a free and simple project management and time tracking application. It allows you to easily create your own projects and tasks, invite people and start working together. (MIT)
Cross-platform
Todoyu is a new, modern and award-winning open source project- and task-management system. Working with todoyu is simple, efficient, time-saving new, modern and straightfoward. (GPL)
Cross-platform
12 applications