Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Leantime - Lean project management for startups & small teams
Redmine - Flexible project management web application
Producteev - Producteev is a free task management application for individuals and teams to collaborate via the web, email, IM, mobile or desktop.
Mantis Bug Tracker - Mantis Bug Tracker is a free and open source, web-based bug tracking system.