Written by a team of German engineers living in Spain, ]project-open[ is one of the most impressive open-source systems I've encountered. (Thanks for pointing it out, Doug Hall.)
]project-open[ in a Nutshell * ]po[ is a Web-based "Enterprise Project Management" software for project-based organizations with 2-200 users. ]po[ integrates areas such as CRM, sales, project planning, project tracking, collaboration, timesheet, invoicing and payments.
* ]project-open[ is one of the largest open-source based web applications in the world with more then 1,000,000 lines of code.
* More then 1000 companies in 25 countries use ]po[ to run their businesses.